The Effectiveness of Psychological Skills Training and Behavioral Interventions in Sport using Single-Case Designs: A Meta Regression Analysis of the Peer-Reviewed Studies

We used a novel meta regression analysis approach to examine the effectiveness of 24psychological skills training and behavioral interventions in sport assessed using single-case 25experimental designs (SCEDs). One hundred and twenty-one papers met the inclusion criteria 26applied to eight database searches and key sport psychology journals. Seventy-one studies 27reported sufficient detail for effect sizes to be calculated for the effects of psychological skills 28training on psychological, behavioral, and performance variables. The unconditional mean 29effect size for weighted (∆ = 2.40) and unweighted (∆ = 2.83 ) models suggested large 30improvements in psychological, behavioral, and performance outcomes associated with 31implementing cognitive-behavioral psychological skills training and behavioral interventions 32with a SCED. However, meta-regression analysis revealed important heterogeneities and 33sources of bias within this literature. First, studies using a group-based approach reported 34lower effect sizes compared to studies using single-case approaches. Second, the single-case 35studies, (over 90 per cent the effect sizes), revealed upwardly biased effect sizes arising from: 36(i) positive publication bias such that studies using lower numbers of baseline observations 37reported larger effects, while studies using larger numbers of baseline observations reported 38smaller – but still substantial – effects; (ii) not adopting a multiple baseline design; and (iii) 39not establishing procedural reliability. We recommend that future researchers using SCED’s 40should consider these methodological issues. 41Keywords: meta regression analysis, psychological skills training, single-case experimental 42designs, procedural reliability, applied sport psychology