GENERALIZABILITY OF THE SCALES OF THE ORIGINAL AND EXPANDED VERSIONS OF THE BRIEF PSYCHIATRIC RATING-SCALE

Generalizability theory was used to examine the reliability of five sc ales derived from the original and expanded versions of the Brief Psyc hiatric Rating Scale with a sample of homeless mentally ill clients. B oth variance due to raters and variance due to items were simultaneous ly evaluated as sources of error (unreliability). The generalizability of the original Thought Disorder, Anxiety-Depression, and Withdrawal scales was adequate, as was the expanded version of the Activity scale . The generalizability of the current Hostility-Suspicion scale was mu ch too low. In general, minimal variance was attributed to raters. Thu s, for most scales, adding items to a scale is a more efficient strate gy for increasing reliability than adding raters.