title: How many therapists? Practical guidance on investigating therapist effects in randomized controlled trials for eating disorders.
abstract: OBJECTIVE
  An important question in implementation/dissemination research is whether the efficacy of a given treatment varies in part based on the therapist delivering the treatment. This study sought to provide practical guidance to researchers in the field of eating disorders for building measurement of therapist effects into the design of a typical, relatively small randomized controlled trial (RCT).
  
  
  METHODS
  Using assumptions based on past trials of eating disorder treatments, Monte Carlo simulations were used to examine 12 different scenarios based on crossing the number of therapists (between two and five) and the estimated therapist effect size (small, medium, and large). Patient sample size and study design were held constant.
  
  
  RESULTS
  There was reasonable power (≥70%) to detect the therapist effect with three or four therapists and a large effect size.
  
  
  CONCLUSIONS
  Several practical implications for testing therapist effects in RCT are discussed.
authors.affiliation: Thompson Research Consulting LLC, Chicago, IL 60601, USA. Doug.thompson@ThompsonResearchConsulting.com
authors.forename: Doug
authors.initials: D
authors.lastname: Thompson
authors.forename: Fary
authors.initials: F
authors.lastname: Cachelin
authors.forename: Ruth H
authors.initials: RH
authors.lastname: Striegel-Moore
authors.forename: Bruce
authors.initials: B
authors.lastname: Barton
authors.forename: Munyi
authors.initials: M
authors.lastname: Shea
authors.forename: G Terence
authors.initials: GT
authors.lastname: Wilson
mesh_terms: D001068:Feeding and Eating Disorders / Q000523:psychology / Q000628:therapy*; D017408:Guidelines as Topic; D006801:Humans; D011613:Psychotherapy; D016032:Randomized Controlled Trials as Topic; D012107:Research Design