Development. The Conners 4–Short was developed following best practices; items from the full-length Conners 4 Parent, Teacher, and Self-Report forms were selected thoughtfully to ensure optimal construct coverage while retaining the psychometric properties of the full-length forms. Shortened scales were developed for the Inattention/Executive Dysfunction, Hyperactivity, Impulsivity, Emotional Dysregulation, and all Impairment & Functional Outcome scales by examining item performance, interrelationships and scale structure, associations with the full-length scales, and relations with criterion variables. Standardized scores (i.e., T-scores and percentiles) were calculated based on the Conners 4 Normative and ADHD Reference Samples. Next, the psychometric properties of the Conners 4–Short were investigated. Detailed information is provided throughout this chapter and is briefly summarized here.

Reliability. Evidence of reliability was established through

• high internal consistency coefficients (e.g., median omega across age groups, raters, and scales within the Normative Samples: Parent = .92, Teacher = .93, Self-Report = .85);

• high degree of test information, mirroring similar trends seen in the full-length Conners 4 scales, providing evidence for precision of measurement;

• statistically significant (p < .001), moderate to strong, and positive test-retest correlation coefficients between scores across a 2- to 4-week interval (Parent: r = .83 to .94, Teacher: r = 78 to .90, Self-Report: r = .52 to .78); and

• strong inter-rater reliability between parent raters (r = .68 to .81), with more modest agreement between teacher raters (r = .21 to .54), and weaker relationships between different types of raters, as they provide meaningfully different perspectives.

Validity. Evidence of validity was established through

• a high degree of association between the Conners 4–Short and the full-length Conners 4 scales (median tau: Parent = .86, Teacher = .88, Self-Report = .86);

• a replication of the internal structure results from confirmatory factor analyses (CFA) which provided evidence to support the structure of the Conners 4–Short scales (final models for the Content Scales had strong fit statistics for all raters [CFI and TLI ≥ .965; SRMR ≤ .044; RMSEA ≤ .059]; final models for the Impairment & Functional Outcome Scales had adequate to strong fit statistics for all raters [CFI and TLI ≥ .958; SRMR ≤ .056; RMSEA ≤ .093]);

• meaningful differences between clinical groups, such that youth with ADHD yield higher scores than both youth from the general population (median Cohen’s d = 1.01 across all raters and scales) and youth with Depression or Anxiety (median Cohen’s d = 0.43 across all raters and scales); and

• moderate to high levels of classification accuracy using scores from the Conners 4–Short to classify youth from the General Population and those with ADHD into their respective groups (overall correct classification rates: 84.9% Parent, 73.8% Teacher, 72.8% Self-Report).

Fairness. Evidence of fairness, in terms of the absence of meaningful psychometric differences, is provided with regard to gender, race/ethnicity, country, and parental education level (PEL):

• Gender. Results provide evidence for the equivalent measurement of males and females. Measurement invariance was supported, there was no evidence of measurement bias (maximum ETSSD = |.08|), and ratings of males and females did not yield significantly different scores on the Parent or Self-Report forms (Cohen’s d = 0.00 to |0.14|). Teachers tended to rate male students higher than female students, with negligible to small effect sizes (Cohen’s d = |0.03| to |0.41|).

• Race/Ethnicity. There was no evidence of measurement bias (maximum ETSSD = |.08|), and measurement invariance was supported across comparisons (ratings of White youth compared to ratings of Black and Hispanic youth). For Hispanic vs. White and Asian vs. White comparisons, no meaningful scale score differences were found between race/ethnic groups across all raters. Scores for Black and White youth did not differ based on Parent or Self-Report ratings, while Teacher ratings yielded small effects on four scales (Cohen’s d = |0.21| to |0.40|), wherein ratings of Black youth resulted in slightly higher scores than ratings of White youth.

• Country of Residence. Results reveal no evidence of measurement bias in terms of country of residence when comparing ratings of youth in the U.S. and Canada on the Conners 4–Short. Assumptions of invariance were upheld, there was no evidence of measurement bias (maximum ETSSD = |.06|), and mean score differences were not statistically significant with negligible to small effect sizes (Cohen’s d = 0.00 to |0.23|).

• Parental Education Level (PEL). Results provide evidence for equivalence between ratings of youth with different levels of parental education on the Conners 4–Short. Assumptions of invariance were upheld, there was no evidence of measurement bias (maximum ETSSD = |.06|), and mean score differences were not statistically significant with negligible to small effect sizes (Cohen’s d = 0.00 to |0.21|).