In the

    United States Court of Appeals
                For the Seventh Circuit
                       ____________________
Nos. 14-3783 & 15-2030
STACY ERNST, et al.,
                                               Plaintiffs-Appellants,

                                 v.

CITY OF CHICAGO,
                                                Defendant-Appellee.
                       ____________________

        Appeals from the United States District Court for the
          Northern District of Illinois, Eastern Division.
          No. 1:08-cv-04370 — Charles R. Norgle, Judge.
                       ____________________

 ARGUED FEBRUARY 25, 2016 — DECIDED SEPTEMBER 19, 2016
               ____________________

   Before BAUER, MANION and KANNE , Circuit Judges.
    MANION, Circuit Judge. After Stacy Ernst and four other
women applied unsuccessfully to work as Chicago paramed-
ics, they brought this Title VII gender-discrimination lawsuit
against the City of Chicago. These women were experienced
paramedics from public and private providers of emergency
medical services; they sought employment as paramedics
with the Chicago Fire Department, but they did not apply to
2                                           Nos. 14-3783 & 15-2030

firefighting positions. All five women were denied jobs be-
cause they failed Chicago’s physical-skills entrance exam.
    In district court, this Title VII case was split into two parts.
The plaintiffs’ disparate-treatment claims went to a jury trial,
in which the district court provided an erroneous jury instruc-
tion. Their disparate-impact claims were tried in a separate
bench trial. This second group of claims turned largely on
whether Chicago’s test was based on a statistically validated
study of job-related skills. We remand for a new jury trial on
the disparate-treatment claims, reverse the bench trial’s ver-
dict on disparate impact because the physical-skills study was
neither reliable nor validated under federal law, and affirm
the evidentiary rulings below.
                            Background
    The Chicago Fire Department employs several hundred
paramedics. 1 When hiring new paramedics, Chicago has not
always tested its applicants’ physical skills. From the 1970s
through the year 2000, paramedics were hired without any
physical test. The hiring process changed in 2000, however,
when Chicago implemented a physical-skills test created for
it by Human Performance Systems, Inc. Deborah Gebhardt,
the president of HPS, led this test-creation process.
   Gebhardt had previously created a physical test for the
Chicago Fire Department’s entry-level firefighters. That test
had a disparate impact on women. The plaintiffs argue that
Chicago’s decision to rehire Gebhardt for the paramedic test,


    1 The factual statements in this opinion are drawn from the record
presented on appeal; they should not be read as binding factual findings
when the plaintiffs’ disparate-treatment claim is retried before a jury.
Nos. 14-3783 & 15-2030                                        3

without taking bids from anyone else, reflects Chicago’s de-
sire to reduce the number of women it hired as paramedics.
    In this case, Gebhardt tested volunteer Chicago paramed-
ics. These were incumbent paramedics working for the Chi-
cago Fire Department. Gebhardt tested these study volun-
teers on physical skills designed to reflect job-related skills.
She tested the paramedics on three “work samples” also de-
signed to reflect job-related skills. Then she compared the re-
sults from the skills testing with the results from the work-
sample testing. Through this process, Gebhardt selected
physical skills that, together, formed Chicago’s physical-skills
entry exam for paramedic applicants. This was a concurrent
validation study, as this opinion will later explain.
    Between 2000 and 2009, nearly 1,100 applicants took
Gebhardt’s entrance examination. Among these, 800 were
men, and 98% of the male applicants passed. Another 300
were women; 60% of female applicants passed. Stacy Ernst,
Dawn Hoard, Katherine Kean, Michelle Lahalih, and Irene
Res-Pullano took the test in 2004, as licensed paramedics with
experience working in other public fire departments or for
private ambulance services. In their daily work, they moved
patients and did so safely. When they took the Chicago phys-
ical-skills examination, however, they all failed.
   After they were denied employment based on their exam
results, Ernst and her fellow plaintiffs filed suit. They chal-
lenged the skills test as discriminatory; they urged that there
was no evidence of Chicago paramedics ever lacking the
physical ability to properly care for their patients. Instead,
they argued, the test was implanted to keep women out. Ulti-
mately, their suit had two parts. On their disparate-treatment
4                                       Nos. 14-3783 & 15-2030

claims, they asked a jury to find that Chicago had a discrimi-
natory motive against women when Chicago implemented its
skills test. On their disparate-impact claims, the plaintiffs ar-
gued in a bench trial that improper statistical methods were
used to establish the skills test.
    The jury instruction on disparate treatment was vigor-
ously debated before both the magistrate judge and the dis-
trict judge. The plaintiffs urged that their burden on this dis-
parate-treatment claim was to prove illegal purpose: that Chi-
cago had a discriminatory intent or motive for implementing
the skills test. When arguing before the magistrate judge, Chi-
cago claimed that the plaintiffs had to satisfy a but-for test:
that Chicago would have hired the plaintiffs if, all other fac-
tors being equal, they were male. In responding to this effort,
the magistrate judge said, “That is absolutely not what this
case is about at all. At all. And you know it.”
    The disparate-treatment jury instruction, labeled Jury In-
struction 24 at all times in this case, included this language
when the magistrate judge settled the instructions:
        Plaintiffs contend the City discriminated
    against them on the basis of sex in violation of Title
    VII of the Civil Rights Act of 1964, as amended. In
    order to succeed on this claim, Plaintiffs must prove
    by a preponderance of the evidence that the City
    intentionally created or used the physical abilities
    test for the purpose of excluding females or reduc-
    ing the number of females who would be hired as
    paramedics by the Chicago Fire Department. The
    City denies that it intentionally created or used the
    physical abilities test to discriminate against female
    applicants.
Nos. 14-3783 & 15-2030                                          5

      It is not enough for Plaintiffs to prove merely
   that the City knew the physical abilities test would
   have an adverse impact on female applicants. An
   adverse impact exists where the rate at which fe-
   male applicants pass the test is substantially less
   than the rate at which male applicants pass. The
   parties do not dispute that the test had an adverse
   impact.
As approved by the magistrate judge, Jury Instruction 24
went on to explain that the plaintiffs should prevail if they
prove by a preponderance of the evidence that Chicago “in-
tentionally created or used” the skills test to “exclude or re-
duce” the women hired as paramedics. If the plaintiffs did not
prove this, however, Chicago must prevail. There was no
problem with the jury instruction on disparate treatment as
established at this point in the litigation.
    Chicago was not done urging the but-for test, however,
and the City successfully resurrected its argument before the
district judge. After a hearing on the matter, the district judge
issued a written order that ruled for the defense. He stated
that “[b]ecause this is ‘an individual action, rather than a class
action, evidence of a pattern of practice can only be collateral
to evidence of specific discrimination against the plaintiff[s].’”
App. 13 (citing Matthews v. Waukesha Cty., 759 F.3d 821, 829
(7th Cir. 2014)) (quotation marks in original). Given this reli-
ance on the individual-action analysis, the district judge
struck the original contents of Jury Instruction 24. He inserted
the pattern instruction on General Employment Discrimina-
tion, so that Instruction 24 now read:
      Each Plaintiff claims that she was not hired as a
   Chicago Fire Department Paramedic because of her
6                                      Nos. 14-3783 & 15-2030

    gender. To succeed on this claim, each Plaintiff
    must prove by a preponderance of the evidence
    that she was not hired by the City of Chicago be-
    cause of her gender. To determine that a Plaintiff
    was not hired because of her gender, you must de-
    cide that the City would have hired the Plaintiff
    had she been male but everything else had been the
    same.
    When the case went to the jury, the jurors expressed con-
fusion over this instruction. After deliberating for 90 minutes,
they sent a note to the district court: “Question to the Judge
regarding instruction 24. Please provide clarification of the
sentence, quote: To determine that a plaintiff was not hired
because of her gender, you must decide that the City would
have hired the plaintiff had she been male but everything else
had been the same.” While the district court and parties were
discussing this, a second note came out: “The jury cannot de-
liberate further without a response to our question. May we
know what the time [is] for a response?” The district court
provided this written response, to which the plaintiffs ob-
jected: “Reread all instructions. The sentence you are asking
to clarify speaks for itself.” Four minutes later, the jury re-
turned a verdict for the defense.
    During the bench trial on disparate impact, the district
court found it clear that the plaintiffs had established a dis-
parate impact on women. The burden therefore shifted to Chi-
cago, which had to prove that its physical-skills test was job-
related and consistent with business necessity. In adopting
Chicago’s proposed conclusions of law, the district court con-
cluded that Gebhardt’s validation study satisfied Chicago’s
burden. The issues at this point in this trial turned on whether
Nos. 14-3783 & 15-2030                                          7

Gebhardt’s study satisfied the law’s technical standards for
validity studies, which appear at 29 C.F.R. § 1607.14(B)(4). The
district court wrote that the “[p]laintiffs’ arguments attacking
Dr. Gebhardt’s job analysis, validation study under the crite-
rion method, and the process of determining the 935 passing
score are unavailing and are rejected.” Dist. Ct. Docket 604 at
2. Accordingly, the burden shifted back to the plaintiffs, who
had to show that Chicago had rejected a substantially equally
valid, but less discriminatory, alternative to the skills test. On
this, the district court concluded that the plaintiffs offered as-
sertions without evidence. The district court thus entered
judgment for Chicago.
    The plaintiffs lost both trials. They now bring this appeal,
which centers on three issues. First, they challenge the dispar-
ate-treatment jury instruction that the district judge gave in
the jury trial. Second, the bench trial on disparate impact
yielded a defense verdict on the statistical methods underly-
ing the skills test, and the plaintiffs challenge those methods.
Third, the plaintiffs argue cumulative error from a series of
evidentiary rulings. We address these issues in turn.
                          Discussion
    The Civil Rights Acts of 1964 and 1991, known collectively
for our purposes as Title VII, prohibit two types of discrimi-
nation. Ricci v. DeStefano, 557 U.S. 557, 577 (2009). First, Title
VII prohibits job-related actions that are motivated by inten-
tional discrimination against employees, based on protected
employee statuses such as race or sex. See id. (quoting 42
U.S.C. § 2000e-2(a)(1)). This is known as disparate treatment.
Plaintiffs must prove that an employer had a discriminatory
motive for taking a job-related action. Id. During the jury trial
in this case, the plaintiffs argued that Chicago adopted its
8                                       Nos. 14-3783 & 15-2030

physical-skills entrance exam in an effort to reduce or elimi-
nate the number of women it hired as paramedics.
    Second, Title VII prohibits employment practices that
have a disproportionately adverse impact on employees with
protected characteristics, even if the impact is unintended. See
id. This is disparate impact. Employers can defend against a
disparate-impact claim by demonstrating that the challenged
practice is job-related for the employee’s position and con-
sistent with business necessity. 42 U.S.C. § 2000e-2(k)(1)(A)(i).
Even if the employer establishes this, however, an employee
can still prevail by proving that the employer has rejected an
available alternative job practice that (1) results in a less dis-
parate impact, and (2) serves the employer’s legitimate needs.
Ricci, 557 U.S. at 578 (citing 42 U.S.C. §§ 2000e-2(k)(1)(A)(ii),
(C)). Chicago does not dispute that its skills test has an ad-
verse impact on women. As Chicago admits, the passing rate
for women is about 60% of the passing rate for men. The par-
ties dispute, however, whether the test is job-related and con-
sistent with business necessity.
    When reviewing claims that a business practice is insuffi-
ciently related to a business necessity, we bear in mind that
“‘[c]ourts are generally less competent than employers to re-
structure business practices, and unless mandated to do so by
Congress they should not attempt it.’” Watson v. Fort Worth
Bank & Trust, 487 U.S. 977, 999 (1988) (quoting Furnco Constr.
Corp. v. Waters, 438 U.S. 567, 578 (1978)).
A. The Disparate-Treatment Claims: Jury Instruction 24
   The plaintiffs begin by appealing the jury instruction on
their disparate-treatment claims. We review jury instruction
challenges de novo. Lewis v. City of Chi. Police Dep’t, 590 F.3d
Nos. 14-3783 & 15-2030                                          9

427, 433 (7th Cir. 2009). District courts have substantial discre-
tion in how to precisely word jury instructions, provided that
the final result, read as a whole, is a complete and correct
statement of the law. Id. We only reverse when jury instruc-
tions are so misleading or confusing that they prejudice a
party. Id. Though we strive for common-sense readings of
jury instructions, and we avoid nitpicking, we also recognize
the importance of getting jury instructions right. See id. Even
when a party fails to object to a jury instruction, a mistaken
instruction is preserved for plain-error review if it impacts
“substantial rights.” Fed. R. Civ. P. 51(d)(2).
    In giving Jury Instruction 24, the district judge relied on
our ruling in Matthews v. Wakesha County, 759 F.3d 821 (7th
Cir. 2014). That case is distinguishable. There, Bernadine Mat-
thews applied for employment as an Economic Support Spe-
cialist or Supervisor in Waukesha County, Wisconsin. Be-
cause she did not satisfy the minimum requirements for either
job, she never received a job offer. Matthews eventually sued
Waukesha County for racial discrimination. She argued that
she should be allowed to bring a Title VII disparate-treatment
claim based, not on evidence of racial discrimination against
her in particular, but on statistics indicating that racial dis-
crimination exists against blacks in general. This is the argu-
ment we rejected in Matthews, where we explained that she
“would need to present evidence indicating that racial dis-
crimination was the employer’s standard operating proce-
dure—the regular rather than unusual practice.” Id. at 829.
This is why we stated that “‘evidence of a pattern or practice
can only be collateral to evidence of specific discrimination
against the plaintiff.’” Id. In Matthews, the plaintiff failed to
present any disparate-treatment claim at all.
10                                      Nos. 14-3783 & 15-2030

    In contrast, the plaintiffs in this case argue that Chicago
created a new standard operating procedure, with the specific
intention of reducing or removing women from among its
new paramedic hires. They do not rely on generalized claims
of statistical bias against women; instead, they argue that
there was no legitimate professional or safety need for Chi-
cago to implement this particular skills test. These arguments
place Ernst and her fellow plaintiffs in a different category
than Matthews. Whether or not they should win, they at least
presented a proper disparate-treatment claim, as indicated by
the district court’s denial of summary judgment. At trial, the
plaintiffs also presented enough evidence to at least support
a correct instruction on disparate treatment.
     Here, the jury should have been instructed on the plain-
tiffs’ burden of proving that Chicago was motivated by anti-
female bias, when Chicago created the entrance exam that
caused these plaintiffs not to be hired. See Ricci, 557 U.S. at
577. Instead, jurors were instructed on a different burden,
which failed to address Chicago’s motive for creating the
skills test: “To determine that a Plaintiff was not hired because
of her gender, you must decide that the City would have hired
the Plaintiff had she been male but everything else had been
the same.” This instruction focused on gender as a factor in
the specific decisions not to hire these five plaintiffs, without
expressly stating the mandatory question: whether Chicago
had an anti-female motivation for creating its skills test. The
magistrate judge’s version of Instruction 24 more accurately
reflected Title VII’s focus on whether there was a discrimina-
tory motive behind Chicago’s conduct. See id.
   This legal error would be enough to establish prejudice,
but the record goes a step further. It shows that the jurors saw
Nos. 14-3783 & 15-2030                                         11

this instruction as the pivotal issue before them, particularly
when they sent a note stating that “[t]he jury cannot deliber-
ate further without a response to our question.” Only four
minutes after the district judge instructed them to take In-
struction 24 at face value, they returned a defense verdict. Un-
der these circumstances, we must remand the disparate-treat-
ment claims for a new trial with proper instruction, namely,
the magistrate judge’s version of Jury Instruction 24.
B. The Disparate-Impact Claims: Validating the Skills Test
    Having addressed the jury instruction on disparate treat-
ment, we turn to disparate impact. The district court found no
problem with Gebhardt’s job analysis and validity study. It
thus entered a verdict for the defense. Because the disparate-
impact rulings were made in a bench trial, we review the dis-
trict court’s legal conclusions de novo and review factual find-
ings for clear error. Bridgeview Health Care Ctr., Ltd. v. Clark,
816 F.3d 935, 937–38 (7th Cir. 2016).
    To prove a disparate-impact case, a plaintiff must show an
adverse impact on employees with a protected characteristic
like gender. Chicago concedes that its physical-skills entrance
test has an adverse impact on women. The burden thus shifts
to Chicago, which must show that its physical-skills testing is
job-related for the employee’s position and consistent with
business necessity. 42 U.S.C. § 2000e-2(k)(1)(A)(i). In this case,
Chicago relies on Gebhardt’s validity study to establish that
its physical-skills test is job-related. Employers are not re-
quired to support their physical-skills tests with formal vali-
dation studies, which “show[] that particular criteria predict
actual on-the-job performance.” Watson, 487 U.S. at 998. When
12                                               Nos. 14-3783 & 15-2030

an employer relies on a validity study, however, federal reg-
ulations establish technical standards for these studies. See 29
C.F.R. § 1607.14(B)(4).
     1. A technical explanation
    Before we analyze the federal regulations on validity stud-
ies, some technical explanation may be useful. We begin this
section by discussing the terms used in federal regulations
and Gebhardt’s validity study, in an effort to help readers
navigate the complex record we are examining. 2
    Validity is the extent to which a study accurately measures
what it sets out to measure. In this case, Gebhardt’s study
sought to measure the physical skills of incumbent Chicago
paramedics. Her study was valid to the extent that it accu-
rately measured their physical skills.
    The type of validity study that Gebhardt chose was a cri-
terion-related validity study. Researchers decide what criteria
they use. Here, Gebhardt solicited job-performance ratings
from the volunteer paramedics’ supervisors and peers. This
was one set of criteria. In addition, Gebhardt created work




    2 We recognize that the court is not a statistical expert, yet we must
also acknowledge that the law mandates statistical discussion in this case.
We therefore note that the terms described here are drawn from federal
regulations, the parties’ briefs, trial testimony, Gebhardt’s statistical re-
port as it appears in the record, and other studies. Our use of technical
terms is also consistent with the use of these terms in previously issued
court rulings. See, e.g., Watson, 487 U.S. at 998 (“formal ‘validation studies’
show[] that particular criteria predict actual on-the-job performance.”);
Guardians, 633 F.2d at 244 (“Criterion-related validity studies correlate test
scores with job performance.”).
Nos. 14-3783 & 15-2030                                          13

samples, which were supposed to represent on-the-job skills.
The work-sample scores were another set of criteria.
    A criterion-related validity study measures a study’s va-
lidity by comparing the assessment-tool results with the cri-
teria. In this case, the assessment tool is a test of physical
skills. Gebhardt would correlate the results of the assessment
tool (the skills-test scores) with the results of the criteria (ei-
ther the job-performance ratings or the work-sample scores).
If there is a strong correlation, the assessment tool is vali-
dated. From a validated study, Gebhardt could conclude that
her skills tests accurately assess test-takers for whether they
have the physical skills that paramedics learn on the job. In
contrast, if there is a weak correlation or no correlation at all,
the assessment tool is not validated. From a study that is not
validated, Gebhardt would not conclude that her skills testing
could assess actual skills learned on the job.
    There are two types of criterion-based validity studies: a
researcher can conduct a predictive validity study or a con-
current validity study. The predictive approach may be some-
what stronger, as suggested by the fact that federal regula-
tions require courts to conduct additional scrutiny into con-
current validity studies. See 29 C.F.R. § 1607.14(B)(4).
    In statistical terms, the difference between predictive and
concurrent validity is simply a matter of timeline. College en-
trance exams like the SAT are examples of predictive studies.
In this model, the SAT is administered to high school stu-
dents, the students who took the SAT attend college, and then
their college GPAs are examined. If there is a significant cor-
relation between the students’ SAT scores and their college
GPAs, the SAT test is considered valid. In this sense, the SAT
scores are tested against the valid college GPAs.
14                                      Nos. 14-3783 & 15-2030

    Here, Gebhardt chose to conduct a concurrent validity
study when she tested Chicago’s volunteer paramedics and
created a physical entrance exam. In a concurrent study, the
researcher takes two measures at the same time. The re-
searcher then uses one measure (which is known to be valid)
to validate the other measure (which needs to be validated).
     First, Gebhardt measured the volunteers’ physical skills
by having them perform physical skills that she determined
were necessary to the paramedic job: a modified stair-climb,
leg lifts, arm-strength tests, and other tests. Gebhardt’s volun-
teer paramedics had higher scores than the scores of other
paramedics in both public-sector and private-sector jobs. The
men in her study could handle an average of 281.9 pounds in
leg-lift tests, for example, while the men in a study of several
hundred paramedics could handle an average of 245.11
pounds in leg-lift tests. Gebhardt stated that this disparity be-
tween volunteers in her study and volunteers in other studies
was “especially” true between the tested female paramedics.
In an effort to soften the Chicago paramedics’ unusually high
scores, Gebhardt added scores from another physical test of
New York City paramedics. She only used the New York City
data, however, when setting a passing score. She did not use
it to validate the Chicago study.
    Second, Gebhardt also created a rating instrument that she
distributed to the volunteers’ supervisors and peers. Because
these volunteers were incumbent Chicago paramedics, she
could obtain on-the-job assessments of these volunteers’ abil-
ities from supervisors and peers who also worked in the Chi-
cago Fire Department. On their own, these ratings would be
a valid assessment of the volunteers’ job skills. Thus,
Gebhardt could compare these supervisor and peer ratings
Nos. 14-3783 & 15-2030                                        15

with her skills tests. If the ratings and the test scores yielded
comparable assessments of the volunteer paramedics, then
Gebhardt could conclude that her skills tests were validated.
    The job-performance ratings and the skills-testing scores,
however, yielded significantly different assessments of the
volunteer paramedics’ on-the-job abilities. Based on supervi-
sor and peer ratings, female paramedics’ performance was
not far from male paramedics’ performance: the average fe-
male rating was 90% to 93% of the average male rating. If the
skills tests were validated by the job-performance ratings,
they would have yielded similar results, with no great dis-
crepancy between female and male skills scores. But in
Gebhardt’s skills test, women performed far less well than
men. On the leg-lift test, for example, the average female score
was 66.4% of the average male score. This discrepancy would
appear to actually invalidate the physical-skills tests.
    Rather than setting aside her original skills tests, and cre-
ating a new set of tests that might better assess paramedic job
skills, Gebhardt provided rationales for setting aside the job-
performance ratings. Gebhardt received ratings for 46 out of
52 volunteer participants. In a study-planning letter to the
Chicago Fire Department, Gebhardt’s company had stated
that a minimum of 110 participants would be necessary to val-
idate this study. Though she had been willing to drop from
110 volunteers to 52, she concluded that she could not go from
52 to 46. Further, when Gebhardt set aside the supervisor and
peer ratings, she replaced them with work-sample scores, as
this opinion will soon explain. But when Gebhardt tested the
reliability of her work samples, she had only 7 volunteers in
the stretcher lift, 17 volunteers in the stair-chair push, and 18
volunteers in the lift and carry. For work samples, she was
16                                      Nos. 14-3783 & 15-2030

comfortable relying on a far smaller number than 46 volun-
teers. This calls into question whether going down to 46 vol-
unteers, with the supervisor and peer ratings, was really the
problem in the researcher’s mind.
    In addition, Gebhardt said that she would have had to
drop the modified stair-climb component of her skills test if
she accepted the supervisor and peer ratings, and women per-
formed better on this stair-climb than on other skills. This cre-
ated the appearance of favoring women, by preserving an as-
pect of the test on which they did well. But because the super-
visor and peer ratings also did not validate other skills tests,
she would also have had to drop skill tests on which women
performed worse than men. The leg-lift, for example, was not
validated by the job-performance ratings. The average female
score on that skills test was 66.4% of the average male score.
Yet Gebhardt ultimately included this skill on Chicago’s en-
trance exam. Thus, though Chicago only claims that Gebhardt
dropped the job-performance ratings in order to preserve
skills testing on which women performed well, the record
conflicts with that narrow version of the facts.
     Regardless of the reasons for setting aside the job-perfor-
mance ratings, Gebhardt still needed a concurrent measure to
validate her skills tests. Thus, she compared the results of the
skills tests with the results of her work-sample tests. She de-
signed three work samples with input from the Chicago Fire
Department: a lift and carry, a stair-chair push, and a stretcher
lift. These work samples were intended to reflect skills that
Chicago paramedics learn on the job.
   In the lift and carry, a volunteer lifted a piece of equip-
ment, carried it up a set of stairs, put it down, lifted another
piece of equipment, carried that down the stairs, and then put
Nos. 14-3783 & 15-2030                                          17

that down. This required five timed cycles, with faster times
resulting in better scores. In the stair-chair push, the volunteer
navigated a stair chair over a ramp, with a dummy seated in
the stair chair. Again, faster times resulted in higher scores. In
the stretcher lift, volunteers lifted a stimulated stretcher to an
arm-locked position, held it for 20 seconds, rested for five sec-
onds, and repeated. The stretcher weighed 90 pounds with
the first lift, and 10 pounds was added each time, up to a max-
imum of 220 pounds. This test continued until the volunteer
completed 13 cycles or could no longer lift the stretcher. Vol-
unteers did not receive higher scores for performing this more
quickly. Instead, scores were based on two measures: cycles
completed and weight lifted.
    When Gebhardt examined the correlation between the
skills tests and the three work samples, she found that three
of the skills were validated: the modified stair-climb, arm-en-
durance test, and leg lift. 3 The correlation between these three
skills and the three work samples exceeded the .01 level of
statistical significance. This means there was a 99% probabil-
ity that the results would repeat if they were tested again—a
statistically rigorous result that exceeds the .05 level required
by law. See 29 C.F.R. § 607.14(B)(5).
    In addition to testing the validity of her study, Gebhardt
tested the reliability of her study. See 29 C.F.R. § 1607.14(C)(5).
An assessment tool is considered reliable if it produces con-
sistent results over time. Gebhardt chose the test-retest relia-
bility approach, in which a researcher administers a test and
then readministers it. If there is a strong correlation between


   3 The remaining skills were not validated by the work samples.
Gebhardt set those skills aside.
18                                        Nos. 14-3783 & 15-2030

the test and retest, the assessment tool is considered reliable.
In technical terms, this process yields what is called a reliabil-
ity coefficient: a number between 0 and 1. If the reliability co-
efficient is 1, there is a perfect correlation between the test and
the retest. This suggests that the assessment tool is highly re-
liable because it produces highly consistent results over time.
Perfectly repeating results, however, are unusual. If the relia-
bility coefficient is 0, there is no correlation between the test
and the retest. This would indicate that the assessment tool is
not reliable at all.
    In this case, Gebhardt provided test-retest reliability re-
sults for the lift and carry (measured by seconds), the stair-
chair push (measured by seconds), the stretcher lift (meas-
ured by weight), and the stretcher lift again (measured by cy-
cles completed). For the lift and carry, the reliability coeffi-
cient was a mere 0.503, indicating about a 50/50 chance that
this test is reliable. For the stair-chair push, the reliability co-
efficient was a moderate 0.743. For the stretcher lift as meas-
ured by weight, the reliability coefficient was a robust 0.982.
And for the stretcher lift as measured by cycles, the reliability
coefficient was 0.978, also indicating strong reliability.
    Based on this work by Gebhardt, Chicago implemented a
physical entrance exam with three components: the modified
stair-climb, arm-endurance test, and leg lift. The passing score
was set with this formula, which favored the modified stair-
climb on which women did well: (7 · modified stair-climb
score) + (2 · arm-endurance score) + (1 · leg-lift score).
     2. An analysis of the validity study
  With that technical explanation, we turn to our analysis.
We consider whether the district court was correct in finding
Nos. 14-3783 & 15-2030                                                    19

that Gebhardt’s job analysis and physical-skills study satis-
fied the express federal regulations on validity studies.
    In the Title VII context, a validity study examines whether
an employer is using an appropriate selection procedure, like
Chicago’s physical entrance examination, in its hiring pro-
cess. See 29 C.F.R. § 1607.5(B). Federal regulations require that
the validity study must establish specific criteria, which em-
pirically demonstrate that the selection procedure predicts or
significantly correlates with important job-performance ele-
ments. 4 29 C.F.R. § 1607.5(B). In this case, the specific criteria
are the physical skills that Gebhardt tested against work sam-
ples, to see whether the skills could be validated as job-related
skills. She ultimately found three valid.
    The technical standards for validity studies are set forth in
29 C.F.R. § 1607.14(B)(4). This section requires that the volun-
teers in a study’s sample population should, as far as possible,
“be representative of the candidates normally available in the
relevant labor market for the job.” 29 C.F.R. § 1607.14(B)(4).
Representativeness is a fact-sensitive inquiry.
   Section 1607.14(B)(4) provides two specific guidelines for
determining whether a sample population is representative. 5

    4 These criteria are deemed “relevant to the extent that they represent
critical or important job duties, work behaviors or work outcomes as de-
veloped from the review of job information.” 29 C.F.R. § 1607.5(B)(2). The
possibility of bias must also be considered when choosing and applying
these criteria. 29 C.F.R. § 1607.5(B)(2).
    5 These are not the only legal issues that Section 1607.17(B)(4) requires
courts to consider, but we conclude that these are the only issues that ap-
ply in the case before us. Gebhardt added scores from a New York City
paramedic study to the scores from her Chicago paramedic study. If she
used the New York data to help validate the Chicago data, we would be
20                                           Nos. 14-3783 & 15-2030

First, we must consider whether the individuals in the sample
population (here, the volunteer incumbent paramedics) are
representative of individuals who are normally available in
the Chicago paramedic market. As far as possible, the sample
population should also include the races, sexes, and ethnic
groups normally available in that job market.
    Second, in a concurrent validity study like this one, we
must examine whether the test focuses on specific skills or
knowledge that are the “primary” focus of skills or
knowledge that Chicago paramedics learn on the job. 29
C.F.R. § 1607.14(B)(4). We note that Title VII regulations do
not provide for employers to implement a general physical
fitness test. Instead, Title VII regulations look for a physical
skills test. These skills must specifically relate to skills that
Chicago paramedics learn in their jobs. Of course, physical
skills may bear a close relationship to physical fitness, but the
entry exam may not merely examine generalized strength.
    With these federal regulations on validity studies, we first
examine whether the volunteer paramedics in Chicago’s
study are representative of individuals who are normally
available in the Chicago job market. See 29 C.F.R.
§ 1607.14(B)(4). The plaintiffs object to the fact that Gebhardt


required to conduct an additional inquiry into questions like whether the
samples are comparable in terms of actual jobs performed. 29 C.F.R.
§ 1607.14(B)(4). There is no indication, however, that she used the New
York data to validate the Chicago study results. Instead, it appears that
she only combined the New York and Chicago data for the purpose of
setting a passing score on the final physical-skills test. And we do not
reach the question of whether Gebhardt set an appropriate passing score.
Thus, we do not conduct additional inquiries into the other issues raised
by Section 1607.17(B)(4), such as actual jobs performed in New York.
Nos. 14-3783 & 15-2030                                                  21

asked existing Chicago paramedics to volunteer, rather than
randomly selecting study participants. This self-selection pre-
sents an obvious concern: when an employer asks its employ-
ees to volunteer for testing, the strongest employees are most
likely to volunteer. Any study results may thus be skewed,
instead of representing the general population. Yet as
Gebhardt explained, people cannot be forced into studies. 6
There are ways to see that, even with volunteer participants,
a study offers legitimate insights into the general population.
On its own, the fact that Gebhardt worked with volunteers is
not a basis for setting aside her study results.
   By Gebhardt’s own testimony, however, these volunteer
paramedics did not represent the skill-set in the general pop-
ulation of Chicago paramedics. Gebhardt testified that the
Chicago volunteers performed better than public-sector and
private-sector paramedics normally perform. In her formal re-



    6 The researcher’s method of selecting volunteers will have significant
implications for how representative a sample population is, and the record
does not address how Gebhardt’s volunteers were chosen, but human par-
ticipants must be willing participants in any event. This is a principle to
which the sciences, social and otherwise, have hewn closely since the Bel-
mont Report was issued in 1979. The Belmont Report was largely a re-
sponse to reports that people were abused in biomedical experiments dur-
ing the Second World War. It established three major principles for stud-
ying humans: respect for persons (protecting individual autonomy), be-
neficence (promoting individual wellbeing), and justice (rendering what
individuals deserve). Under these guidelines, when a person participating
in a study is capable of giving informed consent, the scientist conducting
the experiment should not proceed without it. See Nat’l Comm’n for the
Protection of Human Subjects of Biomedical & Behavioral Research, The
Belmont Report (Apr. 18, 1979), http://www.hhs. gov/ohrp/regulations-
and-policy/belmont-report/index.html#xbasic.
22                                       Nos. 14-3783 & 15-2030

port on this study, Gebhardt forthrightly stated that “the Chi-
cago EMS personnel were found to be above average. This
was especially true for the women.”
    Because she was concerned that the results of her Chicago
study might not be representative, she combined her data on
52 Chicago paramedics with a comparable data-set on 87 New
York City paramedics. As Gebhardt’s study report stated, and
Chicago affirms in its brief, she did this “[t]o avoid artificially
inflating the passing score.” Appellee Br. at 10. In other
words, the New York paramedics presumably had lower
scores than the Chicago paramedics, which helped draw the
average score toward a more normal performance level. For
the combined Chicago and New York City scores to result in
a truly normal or average score, however, the New York City
paramedics’ scores would have to be significantly lower than
normal. There is no evidence—nor would we expect—that the
New York City paramedics perform at a lower skill level than
paramedics who are “normally available in the [Chicago] la-
bor market.” 29 C.F.R. § 607.14(B)(4).
    With 52 Chicago paramedics and 87 New York City para-
medics, Gebhardt had a total sample population of 139 para-
medics. And with this small sample size, the 52 Chicago par-
amedics constituted 37% of the total sample population.
About four in ten paramedics, in the overall sample popula-
tion, were still from Chicago. This is still a sufficiently high
percentage for Chicago paramedics to pull up the average
scores and skew the overall results. Chicago does not explain
why it believes that, by adding 87 New York scores, the prob-
lem of abnormally high scores was resolved. Perhaps this is a
problem that could be resolved by comparing the combined
Chicago and New York results with the studies that Gebhardt
Nos. 14-3783 & 15-2030                                             23

considered, when she concluded that the Chicago volunteer
paramedics had abnormally high scores, and showing that
the combined results are comparable. But the record does not
indicate that even the combined sample population repre-
sents the general paramedic population.
    Second, because this is a concurrent validity study, 29
C.F.R. § 1607.14(B)(4) requires us to examine whether the test
focuses on primary skills learned on the job. In this case, the
entrance exam tests three skills: the modified stair-climb, arm
endurance, and leg lift. These skills were validated by corre-
lating each skill with all three work samples: the lift and carry,
stair-chair push, and stretcher lift. There is a statistically sig-
nificant correlation between these physical skills and these
work samples. In this, the study is fine.
    On the issue of reliability, however, the lift and carry poses
a problem: its reliability score is only 0.503. That is a 50/50
chance of reliability. Federal regulations direct that reliability,
in validity studies like this one, “should be a matter of concern
to the user.” 29 C.F.R. § 1607.14(5). This is particularly true
when the reliability of this lift and carry is equivalent to the
proverbial coin toss: heads, it is reliable; tails, it isn’t. Further,
there was no apparent effort to separate the lift and carry from
the rest of the study. Because each of the three skills (modified
stair-climb, arm endurance, and leg lift) was validated by cor-
relating it against all three work samples (lift and carry, stair-
chair push, and stretcher lift), the unreliability of this lift and
carry undermines all three skills that Chicago tests in its phys-
ical entrance exam. “All tests must be statistically examined
for evidence of reliability before the test developer can estab-
lish the validity of the test.” Gillespie v. Wisconsin, 771 F.2d
1035, 1041 (7th Cir. 1985). Given the lack of reliability in her
24                                      Nos. 14-3783 & 15-2030

study, the test developer in this case cannot establish the va-
lidity of her study.
    Even if reliability was fully established in this case, valid-
ity would be a problem. The plaintiffs legitimately question
whether the work samples themselves are a valid measure of
job skills. The problem here is that Chicago used the work-
sample tests to validate the skills tests—without ever validat-
ing the work samples. As a result, we cannot conclude that
these work samples reflect “the primary focus of” paramedic
skills learned on the job. 29 C.F.R. § 1607.14(B)(4).
    Chicago “would have this court find job-relatedness on
the basis of a high correlation between the results of two sep-
arate testing practices, neither of which by itself has been val-
idated according to accepted methods. We cannot accept this
flawed argument.” Guardians Ass’n of N.Y.C. Police Dep’t, Inc.
v. Civil Serv. Comm’n of the City of New York, 633 F.2d 232, 244
(2d Cir. 1980). In this case, Chicago created a skills test and a
work-sample test, found a strong correlation between the
skills test and the work-sample test, and thus concluded that
the skills test is a good measure of job-related skills. As the
plaintiffs argue, this is a statistical form of self-affirmation.
There is no evidence that the work-sample test, which Chi-
cago used to validate the skills test, is a proper validation of
job skills. On the contrary, we question whether the work
samples actually test the skills that Chicago paramedics learn
on the job, as expressly required by the language of Section
1607.14(B)(4).
    Gebhardt surveyed Chicago paramedics about on-the-job
situations when creating her study. Paramedics indicated
that, when getting to patients, they carry equipment between
10 and 100 feet about 73% of the time. If they carry equipment
Nos. 14-3783 & 15-2030                                         25

upstairs, they climb one or two floors about half the time, and
climb three or four floors about a third of the time.
    Paramedics reported that their patients weighed less than
150 pounds about 24% of the time. Patients weighed 160 to
200 pounds about 40% of the time; 210 to 250 pounds about
another 22% of the time; and 260 or more pounds about 14%
of the time. Chicago paramedics further reported that, if a pa-
tient had to be carried on paramedic equipment, the distance
traveled was less than 100 feet about 80% of the time.
    Gebhardt also found that, when patients were moved into
ambulances, they were in wheeled stretchers about 27% of the
time and in stair chairs about 68% of the time. On the record,
the use of stair chairs in Chicago appears limited. According
to Gebhardt’s findings, stair chairs are used for transporting
patients into ambulances, usually through the side door. She
did not indicate that they were ever used past this point. Ac-
cording to the plaintiffs’ evidence at trial, “they don’t have
ramps at [Chicago] hospitals, and you never push a person
into a hospital on a stair chair.” See Dist. Ct. Docket 554-4 at
665; see also Dist. Ct. Docket 557-1 at 226 (“stair chairs are not
to be used to transport patients from the ambulance to the
hospital under the relevant EMS System Policies and Proce-
dures” and “[p]atients need to be on the stretcher or some-
times secured on the ambulance bench”).
    Given these actual on-the-job skills, it is difficult to see
how all three work samples test job-related skills, much less
skills that are a “primary” focus of skills that Chicago para-
medics learn on the job. See 29 C.F.R. § 1607.14(B)(4). We ad-
dress the work samples in turn, by comparing the work-sam-
ple skills with the skills that paramedics actually use.
26                                     Nos. 14-3783 & 15-2030

    To begin with, the lift and carry seems reasonably job- re-
lated: it tests paramedics’ ability to carry equipment up and
down stairs. The plaintiffs object to the timed nature of this
test. In the context of disparate-impact litigation, the Eighth
Circuit has cast doubt on the value of timed physical-skills
testing. As it said, “where hiring is contingent upon test per-
formance, applicants tend to work as fast as possible during
the test in order to outperform the competition.” E.E.O.C. v.
Dial Corp., 469 F.3d 735, 739, 742–43 (8th Cir. 2006). And as
Gebhardt’s own study report recognized, “physical test cutoff
scores should be set at the minimum acceptable level,” not at
the maximum level, because the goal is to identify people
with sufficient physical skills. Further, faster performance is
not always the most careful performance. We can see where
some speed, though not excessive speed, may be job-related
for paramedics who answer time-sensitive emergency calls.
But in staying faithful to the record, we do not have the infor-
mation necessary to analyze and reach a conclusion on the ap-
propriateness of this timed test. Regardless of how appropri-
ate it was to time the lift and carry, this work sample did not
prove reliable. And an unreliable assessment tool cannot be
validated. Gillespie, 771 F.2d at 1041.
    Next, the stair-chair work sample focuses on pushing a
stair chair through a course and over a ramp. The plaintiffs
also object to the timed nature of this test, but again, we lack
the information needed to reach a conclusion on timing. We
do recognize that stair chairs are, as their name suggests, de-
signed to be carried up and down stairwells. The record indi-
cates that there are no ramps leading into Chicago hospitals.
Even if there were ramps, Chicago paramedics may not
transport patients into hospitals using stair chairs. The record
does not indicate that the stair chairs in the work sample were
Nos. 14-3783 & 15-2030                                        27

transported for the same distances as stair chairs in real para-
medic situations, which casts doubt on this work sample, too.
We do not conclude, however, that the stair-chair work sam-
ple is necessarily unrelated to on-the-job skills.
    Moving to the final work sample, we must conclude that
the stretcher lift does not resemble skills learned on the job.
Real paramedics raise a stretcher and then move. We question
why paramedics in the work sample have their arms
“locked.” Regardless, when paramedics transport a real pa-
tient, they do not cycle the patient-laden stretcher up and
down, and the record shows that they typically travel less
than 100 feet. It is hard to imagine paramedics requiring
nearly four-and-a-half minutes to cross 100 feet. Yet the rec-
ord indicates that paramedics in the stretcher-lift sample had
a different task: they had to complete 13 cycles up and down,
which requires a total of 4 minutes and 20 seconds to com-
plete, even with rest times omitted.
     Further, stretchers are usually carried by at least two par-
amedics and/or wheeled, while the stretcher-lift work sample
requires one paramedic to carry all the weight alone. At the
beginning of the stretcher-lift work sample, paramedics are
lifting 90 pounds alone. This is the equivalent of carrying a
180-pound patient in tandem. By the end of this lift work sam-
ple, the paramedic is lifting 220 pounds alone. This is the
equivalent of carrying a 440-pound patient in tandem, imme-
diately after carrying 12 other patients who were increasingly
heavy. There may be situations when paramedics transport
more than a dozen patients in rapid succession, where most
of the patients are atypically heavy individuals, but this is not
within the scope of “primary” EMS skills. See 29 C.F.R.
28                                      Nos. 14-3783 & 15-2030

§ 607.14(B)(4). For this work sample, the simulated job skills
and real job skills are different in description.
    In comparing the skills that Chicago paramedics learn on
the job with the skills that Gebhardt’s three work samples re-
quire, we must conclude that these are two different sets of
skills. Even if they were the same, the work-sample skills are
more taxing than real on-the-job skills. Gebhardt has test sub-
jects cycling abnormally heavy stretchers up and down for 4
minutes and 20 seconds, for example, even with rest times
omitted. In contrast, paramedics usually transport relatively
lighter stretchers across a distance of 100 feet or less, which
should require substantially less than 4 minutes. And as one
of our sister circuits has affirmed, plaintiffs should prevail on
their disparate-treatment claim when a physical-skills en-
trance exam is “significantly more difficult than the actual job
workers performed at the plant.” Dial, 469 F.3d at 739, 742–43.
The difficulty of these work samples also undermines Chi-
cago’s argument that these work samples represent real skills
that Chicago paramedics learn on the job.
    In this case, at least two out of three work samples are not
valid. The validity of the three skills that are tested in Chi-
cago’s entrance examination, however, depends on all three
work samples being valid. This undermines the entire physi-
cal-skills entrance test that Chicago administers.
    The physical entrance exam that resulted from this study
of volunteer paramedics risks cementing unfairness into Chi-
cago’s job-application process. Unfairness is defined this way:
when women characteristically obtain lower scores on the
physical entrance exam than men, and the score differences
“are not reflected in differences in a measure of job perfor-
mance,” the entrance exam is unfair. See 29 C.F.R.
Nos. 14-3783 & 15-2030                                           29

§ 1607.14(B)(8)(a). We recognize that, in itself, there is nothing
unfair about women characteristically obtaining lower physi-
cal-skills scores than men. But the law clearly requires that
this difference in score must correlate with a difference in job
performance.
    To guard against this unfairness, the law requires that the
physical exam must validly test job-related skills. We recog-
nize that, if men and women have adequate physical skills to-
gether, patients can benefit from coed paramedic teams. The
minimum requirement is adequacy, not superiority. See Lan-
ning v. Se. Pa. Transp. Auth., 308 F.3d 286, 287 (3d Cir. 2002)
(affirming that, in a disparate-impact claim, “a discriminatory
cutoff score on an entry level employment examination must
be shown to measure the minimum qualifications necessary
for successful performance of the job”). Perhaps mixed-gen-
der teams could offer patients a more diverse combination of
physical and psychological care than single-gender teams. A
female paramedic might fit into a space where a male para-
medic does not; a female victim might be helped by having a
female paramedic on the team. And in this case, the validated
testing of job-related skills simply is not there: it is not enough
to show a strong correlation between two tests that Chicago
created concurrently. To validate the other test, at least one
test must itself be a valid measure of job skills.
    Accordingly, on this detailed review of the record, we con-
clude that there is clear error in the factual conclusions
reached below. Under the federal requirements for validity
studies articulated in 29 C.F.R. § 1607.14(B)(4), clear problems
arise with the job analysis, the reliability of this validity study,
and the validation of Chicago’s validity study. Chicago failed
30                                               Nos. 14-3783 & 15-2030

to establish that its physical-skills entrance test reflects “‘im-
portant elements of job performance.’” Dial, 469 F.3d at 743
(quoting 29 C.F.R. § 607.5(B)). And this lack of connection be-
tween real job skills and tested job skills is, in the end, fatal to
Chicago’s case. Thus, the plaintiffs should have prevailed on
their Title VII disparate-impact claims. 7
C. Disparate Treatment and Impact: Evidentiary Rulings
    Finally, the defendants object to evidentiary rulings made
below. We address these briefly, bearing in mind that the
standard of review for evidentiary rulings is abuse of discre-
tion, and we affirm the evidentiary rulings appealed here. See
Bradley v. Work, 154 F.3d 704, 708–09 (7th Cir. 1998).
    First, during the disparate-treatment trial, the district
court admitted handwritten committee notes under the busi-
ness-records exception. These notes were written by Deputy
Fire Commissioner Derrick Jackson during a Chicago Fire De-
partment committee discussion about physical injuries that
Chicago’s paramedics sustained on the job. First Deputy
Commissioner Charles Stewart authenticated the handwrit-
ing as Jackson’s. He further testified that, as part of its regular
business practices, the Chicago Fire Department maintains
committee-meeting notes like Jackson’s notes.



     7 The plaintiffs also challenge the passing score established for this
skills test, by arguing that there is no appropriate statistical basis for set-
ting the cut-off score. Because this particular test is not validated, how-
ever, we do not address the statistics behind the passing score.
    Chicago did not carry its burden of proof on the test-validation issue,
so we also do not reach the parties’ arguments regarding less-discrimina-
tory alternatives to the test.
Nos. 14-3783 & 15-2030                                       31

     Meeting minutes properly fall within the business-records
exception. United States v. Borrasi, 639 F.3d 774, 779 (7th Cir.
2011). Federal Rule of Evidence 803(6) requires, among other
things, that these notes must be made during or near the time
of the meeting by someone with knowledge. The notes must
also be maintained in the regular course of business. The dis-
puted evidence satisfies Rule 803’s requirements. The plain-
tiffs rely on United States v. Borrasi, however, where we ex-
cluded evidence of a committee report that was discussed in
committee minutes. See id. at 779–80.
    In Borrasi, we concluded that “[t]hose reports and any
statements therefrom are hearsay, as each comprises state-
ments written by [individuals] not testifying before the court
that [a party] wished to introduce for the truth of the matters
asserted.” Id. Borrasi is distinguishable. There, the moving
party sought to admit a report through the committee notes.
Here, Chicago sought to admit evidence of what was dis-
cussed in the committee meeting itself. This was proper.
    Though the plaintiffs object to Chicago admitting the evi-
dence through Stewart, saying that Stewart never attended
the meeting in question and could not be cross-examined
about the meeting, Stewart’s role was simply to authenticate
the business-record evidence. If the plaintiffs wished to cross-
examine Jackson, they could have subpoenaed him as a wit-
ness. The district court did not abuse its discretion.
   Second, during the disparate-treatment trial, the plaintiffs
sought to admit evidence that Gebhardt had previously en-
gaged in conduct that reduced the number of jobs for which
women qualified. The district court would not let them offer
evidence that Gebhardt’s work adversely affected women. It
32                                       Nos. 14-3783 & 15-2030

allowed Gebhardt to provide this compelling testimony, how-
ever, regarding the purpose of her entire career:
         Question: What is the purpose in your mind of
     your entire career with respect to developing and
     validating physical abilities tests for physically de-
     manding jobs?
         Answer: Well, it’s to actually give women a shot
     at a physically demanding job. And it occurred
     when I first started doing this, I was doing a project
     for AT&T. And women wanted to work in what’s
     called the outside craft positions. They were work-
     ing clerical, and the pay was a lot better for outside
     craft….
        One of the things I saw was that the women
     could do the jobs…. And I also saw in my early
     years that employers said: Oh, well we want to get
     women into these jobs.
        So what happens is they just put them in the
     jobs…. the men were like: Oh, it’s nice you’re here.
        And then they became resentful of the fact that
     some of the women—not all, but some—could not
     handle the physical demands….
        So what we had was when we started putting in
     the physical abilities tests, we found that one, the
     women could meet the physical demands and they
     were much more accepted by their peer—male
     peers when they could actually perform the tasks.
     And that was a good thing because in the early
     years, they got a bad attitude towards it.
Nos. 14-3783 & 15-2030                                       33

       So to suggest that I would discriminate against
   women is absurd because I’ve spent most of my life
   trying to make sure that women are successful in
   these jobs.
Dist. Ct. Docket 554-9 at 26–27. With the defense offering this
evidence about the purpose of Gebhardt’s “entire career,” the
plaintiffs should also be allowed to offer evidence that rebuts
her testimony. Only permitting evidence on one side of this
equation would be unfairly prejudicial. The plaintiffs do not
provide specific explanations, however, of what they tried to
admit into evidence and why the district court ruled against
them. As a result, the objection is undeveloped and is thus
waived for purposes of the first jury trial.
    Third, the plaintiffs sought to admit evidence that the Chi-
cago Fire Department offers more pretest training to its fire-
fighter applicants than its paramedic applicants. Once again,
however, the plaintiffs offer a generalized objection. They do
not claim that the two tests are comparable. Nor do they ex-
plain why the Chicago Fire Department should approach two
tests in the same way. On the face of the matter, it is reasona-
ble for an employer to have different hiring practices for dif-
ferent positions. Again, this objection is undeveloped, and we
find that it is waived for the first jury trial.
    The remaining objections appear to be against evidentiary
rulings made during the bench trial on disparate impact. Be-
cause we conclude that the concurrent validity study was not
validated, we do not address these rulings.
34                                      Nos. 14-3783 & 15-2030

                          Conclusion
    The disparate-treatment claims are REMANDED for a new
trial, with directions to read the original version of Jury In-
struction 24. The disparate-impact trial verdict is REVERSED,
with instructions to enter judgment in the plaintiffs’ favor. Fi-
nally, the evidentiary rulings below are AFFIRMED.