Internal Consistency. There is evidence of excellent internal consistency of the Conners 4 Parent, Teacher, and Self-Report scale scores.

• Median omega coefficient in the Normative Samples: Parent = .94, Teacher = .95, Self-Report = .90.

• Standard error of measurement (SEM) is low for Conners 4 scales and across raters (median SEM in the Normative Samples: Parent = 2.60, Teacher = 2.36, Self-Report = 2.36). The low values indicate very little error in the estimated true scores.

Test Information. Precision is high for the target ranges of the test information functions (TIF), indicating sufficient measurement precision and low conditional standard error of measurement, providing additional evidence for the reliability of the Conners 4 scales.

Test-retest reliability: There is evidence that the Conners 4 scales have excellent test-retest reliability (median r: Parent = .94, Teacher = .90, Self-Report = .75). The stable nature of the scores provides assurance that changes observed in scores over time are due to a true change in the symptom, feature, or impairment, rather than to imprecise measurement.

Inter-Rater Reliability: Moderate to strong relationships were found between same rater types, while weaker relationships were found across different rater types. These results serve to highlight the importance of examining information from multiple sources when conducting a comprehensive assessment.

• Same Rater Type. When two parents rate the same child, there is evidence of moderate to strong relationships in scores (median r = .84). In contrast, when two teachers rate the same student, there are more moderate associations across the Conners 4 scale scores (median r = .52).

• Different Rater Types. While there are mostly moderate associations between scores when a parent and a teacher rate the same youth (median r = .45), differences are more pronounced when comparing youth self-reports to parent or teacher raters (Parent/Self-Report median r = .33; Teacher/Self-Report median r = .23).

• Results of the inter-rater study also highlighted that youth are far more likely to disclose about self-harming behaviors (19.4%) than parents (8.1%) or teachers (1.8%) who may not be aware of these behaviors.