Designed three-factor experiment to evaluate potential for improving first-session performance of six trainee-therapists as measured by postsession client ratings (n=48). Rather than through standardizing therapist behavior by using training manual beforehand, therapist effects were handled through statistical control. Found that more frequent…

In a randomized clinical trial, a researcher can increase statistical power by including a covariate (or pretest) to reduce participants; however, this raises the cost per participant. A simple closed form expression is derived that applied researchers can use to answer the cost/benefit question. (JPS)