distress and true distress among those with major problems in life, but the NIM scale can help distinguish
between the two. In contrast, positive impressions represent ‘the presentation of a very favorable impression or
the denial of relatively minor faults’ (p. 30). Non-clinical samples normally endorse more items on the PIM scale
than do clinical samples. High scores can have several interpretations: a true absence of minor faults, or an
attempt to appear as having few faults, or an absence of awareness of personal weaknesses. These definitions are
generally in keeping with other definitions of underreporting and over-reporting. There is no implication as to
whether these tendencies represent conscious attempts to present a false or distorted picture of the self or
whether they reflect aspects of an underlying personality of which the person may have limited conscious
awareness.
Description
The PAI was constructed on the basis of construct-oriented principles of test development. As such, each item
is intended to have a demonstrable link to the underlying construct. Morey acknowledges the influence of
Jackson (1970) and the principles of test development outlined therein. The items use a four-alternative response
format: False ,Not at All True; Slightly True; Mainly True; and Very True . The NIM scale has nine items, all true-
keyed. Similarly, the PIM scale contains nine items, eight of which are false-keyed with one true-keyed item.
Items on both scales are spread throughout the item booklet.
Sample
The standardization sample is a subset of a group of 1462 community dwelling adults over the age of 18 years.
Twelve U.S. states were used, and a census-matched sample of 1000 individuals was selected to match the vari-
ables of gender, race, and age with the U.S. Census for 1995. The PAI manual reports raw score means of 1.69
(SD52.70) for the NIM scale and 15.07 ( SD54.36) for the PIM scale. An additional sample of 1051 university
students from seven American universities is also reported in the PAI manual. The raw score mean for that
group for the NIM scale is 1.50 ( SD52.20), with a mean of 13.08 ( SD54.36) for the PIM scale. A clinical sample
of 1265 patients from 69 clinical sites is also reported. In this group, the raw mean score for the NIM scale was
4.38 ( SD54.27) with a corresponding mean of 12.24 ( SD55.07) for the PIM scale. The growing research literature
on the PAI provides further information on scores of the NIM and PIM scales in specific groups such as criminal
defendants ( Kucharski & Duncan, 2007 ).
Reliability
Internal Consistency
Cronbach alpha coefficients for the NIM scale score range from .63 in the college sample to .74 in the clinical
sample. Alpha coefficients for the PIM scale score range less broadly, from .71 in the census-matched sample to
.77 in the clinical sample. The manual cites eight other studies that report alpha coefficients for the NIM scale
score ranging from .45 to .77 with a mean of .60, while alpha coefficients for the PIM scale score range from .58
to .80 (mean 5.73). The PIM and NIM scales are relatively short at nine items each, and have a diverse range
of content.
Test/C0Retest
The manual ( Morey, 2007 ) reports on two samples providing test /C0retest reliability. The first was on 75 adults
from the community, tested an average of 24 days apart. The second sample comprised 80 University students
tested four weeks apart. Stability coefficients for the NIM scale score were .71 and .80, respectively. Likewise, sta-
bility coefficients for the PIM scale score were .81 and .75, respectively.
Validity
Convergent/Concurrent
The manual ( Morey, 2007 ) reports validity correlations of the NIM scale with scores from the MMPI-2 validity
scales, MCMI-II validity scales, the Marlowe /C0Crowne Social Desirability Short Form and the SIRS. The validity
correlations are invariably in the predicted direction, with the exception of correlations with the MMPI Lscale.
The same constellation of validity evidence is reported in the manual ( Morey, 2007 ) for the PIM scale score. PIM
raw scores show a steady increase in mean value, from the clinical sample to the normal sample to a group
instructed to fake good. Correlations with a variety of other validity scale scores are reported as well.
Correlations with scores from the MMPI validity scales are all substantial and in the predicted directions.33 MEASURES OF OVER-REPORTING
I. INTRODUCTION: CORE ISSUES IN ASSESSMENT