Effect Size Guidelines for Individual and Group Differences in Physiotherapy.

Abstract

To investigate the distribution of effect sizes in individual and group differences within physiotherapy to provide standardized estimates of effect sizes in the field. Meta-analysis of effect sizes extracted from published studies in physiotherapy. Data were collected from 6 physiotherapy journals with the highest H-index. A total of 111 meta-analyses (N=111) were analyzed, yielding 3374 extracted effect sizes. Not applicable. Effect sizes were categorized as diagnostic methods, kinesiotherapy, manual therapy, and a group labeled "laser therapy, magnetic therapy, electrotherapy, etc." Hedges' g effect sizes were determined, and percentiles were calculated to establish thresholds for small, medium, and large effects. For individual differences (Pearson's r), the 25th, 50th, and 75th percentiles were 0.33, 0.45, and 0.62, respectively. For group differences (Hedges' g), these values were 0.13, 0.35, and 0.79, respectively. In kinesiotherapy, small, medium, and large effect sizes were determined as 0.1, 0.3, and 0.7, respectively. For physiotherapy diagnostics, the thresholds were 0.2, 0.5, and 1.0, respectively. For physical treatments such as laser therapy, magnetic therapy, and electrotherapy, the corresponding values were 0.1, 0.4, and 1.1. For manual therapy, the thresholds were 0.1 for small effects, 0.3 for medium effects, and 0.8 for large effects. For individual differences (Pearson's r), small, medium, and large effect sizes should be considered 0.3, 0.5, and 0.6, respectively. For group differences (Cohen's d or Hedges' g), small, medium, and large effect sizes should correspond to 0.1, 0.4, and 0.8, respectively. These findings provide standardized effect size estimates for various physiotherapy interventions, aiding in the interpretation of research outcomes.