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Table 1 Interpretive guideline for Conners’ T scores and percentiles

From: Protocol for the STAR (Sheffield Treatments for ADHD) project: an internal pilot study assessing the feasibility of the Trials within Cohorts (TwiCs) design to test the effectiveness of interventions for children with ADHD

T score Percentile Guideline
70+ 98+ Markedly atypical (significant problem)
66–70 95–98 Moderately atypical (significant problem)
61–65 86–94 Mildly atypical (possible problem)
56–60 74–85 Slightly atypical (borderline)
< 30–55 < 2–73 Average (typical: should not raise concern)