A comparison of six measures of working alliance.

Compared 6 measures of working alliance: the California Psychotherapy Alliance Scales (CALPAS), the Penn Helping Alliance Scales (PHAS), the Vanderbilt Therapeutic Alliance Scale (VTAS), Working Alliance Inventory—Observer Form (WAI—O), Working Alliance Inventory—Client Form, and Working Alliance Inventory—Therapist Form. All measures had high internal consistency. Observers were able to reach high levels of interrater reliability on all the observer-rated measures (CALPAS, PHAS, VTAS, WAI—O). Evidence of construct validity was found for the CALPAS, VTAS, and WAI—O, given that they were all highly correlated with each other. (PsycINFO Database Record (c) 2010 APA, all rights reserved)