Reliability
Internal Consistency
Cronbach alpha coefficients for the eight domain scales of SDQ-I range from .80 to .90 in the normative sample
as reported in the manual ( N53,562; Marsh, 1992a ). The alpha coefficient for the global scale was .81 based on
739 participants ( Marsh, 1992a ). The range of alpha coefficients reported in the test manual for the 10 domain
scales of the SDQ-II was .83 to .90 and for the global self-esteem estimate .88 ( N54,494; Marsh, 1992b ). For the
SDQ-III, the range of alpha coefficients reported for the 12 domain scales was .75 to .95 (Marsh & O’Neill, 1984).
Similar coefficients for the SDQ scales (ranging from .76 to .95 with a mean of .90) were reported in Byrne (1996,
pp. 199 /C0200). In addition, Boyle (1994) provided a favorable evaluation of the SDQ-II and suggested that the
item content was not unduly narrow or redundant as to generate concerns about attenuated predictive validity
coefficients (see Boyle, 1991 for a detailed description of this issue).
Test/C0Retest
Test/C0retest reliability information for the SDQ-I is available in Blascovich and Tomaka (1991, p. 145) . Stability
coefficients for the SDQ-I scales across an interval of about six months were reported in Marsh, Smith, Barnes,
and Butler (1983) . The mean stability coefficient was .61 for a combined sample of 671 students in fourth to sixth
grade. Stability coefficients for the SDQ-II scales across a 7-week interval for 137 female students were reported
inMarsh and Peart (1988) , ranging from .72 to .88 (median 5.79). Similar levels of reliability were reported for
the SDQ-II short-form ( Marsh et al., 2005a,b ) using a sample of 3,731 adolescents who completed assessments at
three time points during the academic year. The average stability coefficients for the short-form ranged from .62
(Time 1 to Time 3) to .72 (Time 2 to Time 3) and these values remained largely unchanged when coefficients
were corrected for measurement error (.68 and .79). Short-term stability coefficients for the SDQ-III have been
reported for 361 participants in an Outward Bound course ( Marsh, Richards, & Barnes, 1986 ), with stability coef-
ficients across a one-month interval ranging from .77 to .94 (median 5.87).
Validity
Marsh and colleagues have accumulated much validity inf ormation for the SDQ instruments. A good starting point
for this literature is the extensive reviews by Boyle (1994) ,Byrne (1996) ,Marsh (1990a) ,a n d Marsh and Craven (2006) .
Convergent/Concurrent
Scores on general self-esteem scales of the SDQ-III are strongly associated with the RSE. For example, Marsh,
Byrne, and Shavelson (1988) reported a correlation of .79 between the RSE and the SDQ-III general scale based on
a dataset of 991 Canadian high school students (.87 when adjusted for attenuation due to measurement error).
Marsh (1992a) reported that the SDQ-I general scale correlated .57 with the Harter global scale in a sample of 508
Australian students in 7th through 9th grades (.69 when corrected for attenuation). Further evidence based on
specific domain correlations suggests that the SDQ and Harter scales measure similar content. The corresponding
scales measuring physical self-concept correlated .67 and the scales measuring peer relations correlated .74
(Marsh, 1992a ). The correlation between self-reported and inferred general self-esteem (i.e., self-esteem rated by
an outside informant) was .41 and .58 for the domains for the SDQ-III ( Marsh, 1992b ). Marsh and his colleagues
have linked academic achievement to specific domains of the SDQs (e.g., Marsh & Craven, 2006 ). For example,
Marsh et al. (1988) reported a correlation of .55 between mathematics self-concept and mathematics achievement
test scores and a correlation of .24 between verbal self-concept and verbal achievement. Marsh and Peart (1988)
reported that a performance based composite of physical fitness correlated positively with physical ability self-
concept scores from the SDQ-II ( r5.45) in an Australian sample of 137 8th grade girls.
Divergent/Discriminant
As an example of divergent validity, the SDQ general self scale correlates negatively with measures of negative
mood states including anxiety as measured by Spielberger’s State /C0Trait Anxiety Inventory ( r52 .51,N5130,
Marsh, 1992b ).
Construct Factor Analytic
Marsh initially used item pairs or parcels in all exploratory and confirmatory factor analyses (see Byrne, 1996 )
on the logic that item pairs are more reliable than single items and offer some convenience to researchers by
reducing the number of indicators. Marsh (1992a) reported the results of an initial exploratory factor analysis of
the SDQ-I with an oblique rotation based on 3,562 responses from his normative database. Factor coefficients148 6. MEASURES OF SELF-ESTEEM
II. EMOTIONAL DISPOSITIONS