Self‐rated and clinically assessed psychopathy: Same or different thermometers?

Purpose To examine whether scores on a self‐report instrument can serve as a valid proxy for clinically assessed psychopathy. Method Using data from the Pathways to Desistance study, we applied a hybrid NEAT (non‐equivalent groups with anchor test)–SG (single group) equating design to link the Psychopathy Checklist–Youth Version (PCL–YV) with the Youth Psychopathic Traits Inventory (YPI). The precision and accuracy of the equated scores were evaluated in three ways: (1) by computing the standard error of equating (SEE), (2) by assessing their correspondence with observed PCL–YV scores as the criterion and (3) by identifying the score range in which the two scales correlated most strongly. Results SEE values indicated that the equated scores were tightly clustered, reflecting high precision. However, the equated scores deviated substantially from the observed scores, indicating poor accuracy. Within the clinically important range near the conventional PCL–YV threshold of ≥30, equated and observed scores were unexpectedly negatively correlated. Conclusion These findings suggest that conditions more stringent than equating precision alone must be met before a self‐report scale can be considered a valid screening tool for clinically significant psychopathy.