ABSTRACT
The original version of this article unfortunately contained a mistake. In Results section, under the heading the "Application", CI difference values were incorrect in one of the sentences. The corrected sentence is given below.
ABSTRACT
This paper aims to provide researchers with practical information on sample sizes for accurate estimations of therapist effects (TEs). The investigations are based on an integrated sample of 48,648 patients treated by 1800 therapists. Multilevel modeling and resampling were used to realize varying sample size conditions to generate empirical estimates of TEs. Sample size tables, including varying sample size conditions, were constructed and study examples given. This study gives an insight into the potential size of the TE and provides researchers with a practical guide to aid the planning of future studies in this field.
Subject(s)
Clinical Trials as Topic/methods , Clinical Trials as Topic/standards , Mental Disorders/therapy , Professional-Patient Relations , Psychotherapy/methods , Psychotherapy/standards , Adolescent , Adult , Aged , Clinical Competence , Female , Humans , Male , Middle Aged , Reproducibility of Results , Sample Size , Young AdultABSTRACT
Most research on the dose-effect model of change has combined data across patients who vary in their total dose of treatment and has implicitly assumed that the rate of change during therapy is constant across doses. In contrast, the good-enough level model predicts that rate of change will be related to total dose of therapy. In this study, the authors evaluated these competing predictions by examining the relationship between rate of change and total dose in 4,676 psychotherapy patients who received individual psychotherapy. Patients attended 6.46 sessions on average (SD = 4.14, range = 3-29, Mdn = 5). The results indicated that although patients improved during treatment, patients' rate of change varied as a function of total dose of treatment. Small doses of treatment were related to relatively fast rates of change, whereas large doses of treatment were related to slower rates of change. Total dose had a nonlinear relationship with the likelihood of clinically significant change. Given the variability in rates of change, it appears that time limits for treatment uniform to all patients would not adequately serve patients' needs.
