title: Reliability of Therapist Effects in Practice-Based Psychotherapy Research: A Guide for the Planning of Future Studies.
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.
authors.affiliation: Clinical Psychology and Psychotherapy, Department of Psychology, University of Trier, 54286, Trier, Germany. schiefele@uni-trier.de.
authors.forename: Anne-Katharina
authors.initials: AK
authors.lastname: Schiefele
authors.affiliation: Clinical Psychology and Psychotherapy, Department of Psychology, University of Trier, 54286, Trier, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lutz
authors.affiliation: University of Sheffield, Sheffield, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Barkham
authors.affiliation: Clinical Psychology and Psychotherapy, Department of Psychology, University of Trier, 54286, Trier, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Rubel
authors.affiliation: Mental Health and Addiction Research Group, Hull York Medical School & Department of Health Sciences, University of York, Heslington, UK.
authors.forename: Jan
authors.initials: J
authors.lastname: Böhnke
authors.affiliation: Leeds Community Healthcare NHS Trust and Department of Health Sciences, University of York, Heslington, UK.
authors.forename: Jaime
authors.initials: J
authors.lastname: Delgadillo
authors.affiliation: University of Evansville, Evansville, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Kopta
authors.affiliation: Ruhr-Universität Bochum, Bochum, Germany.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Schulte
authors.affiliation: University of Sheffield, Sheffield, UK.
authors.forename: David
authors.initials: D
authors.lastname: Saxon
authors.affiliation: Brigham Young University, Provo, USA.
authors.forename: Stevan L
authors.initials: SL
authors.lastname: Nielsen
authors.affiliation: Brigham Young University, Provo, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lambert
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002983:Clinical Competence; D002986:Clinical Trials as Topic / Q000379:methods* / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000628:therapy*; D008875:Middle Aged; D011369:Professional-Patient Relations; D011613:Psychotherapy / Q000379:methods* / Q000592:standards*; D015203:Reproducibility of Results; D018401:Sample Size; D055815:Young Adult
keywords: Multilevel analysis; Naturalistic data; Practical guide; Sample size; Therapist effects