All effect sizes were calculated based on mean scores and standard deviations. Following the recommendations ofthe relevant literature, effect size (d) was calculated as follows: (a) for studies using postintervention measures for experimental and control groups, the typical standardized mean differences were computed using group means and the pooled standard deviation (Cohen, 1987); (b) for studies using pre- and postinterventions measures for experimental and control groups, the standardized mean difference in change scores (from pre- to posttest) were computed using the pooled pretest standard deviation (Morris, 2008); (c) for studies using pre- and postintervention measures for experimental group only (including studies using singlesubject multiple-baseline designs), the standardized mean change was computed using the pretest standard deviation (Hojat & Xu, 2004).
All effect sizes were calculated based on mean scores and standard deviations. Following the recommendations ofthe relevant literature, effect size (d) was calculated as follows: (a) for studies using postintervention measures for experimental and control groups, the typical standardized mean differences were computed using group means and the pooled standard deviation (Cohen, 1987); (b) for studies using pre- and postinterventions measures for experimental and control groups, the standardized mean difference in change scores (from pre- to posttest) were computed using the pooled pretest standard deviation (Morris, 2008); (c) for studies using pre- and postintervention measures for experimental group only (including studies using singlesubject multiple-baseline designs), the standardized mean change was computed using the pretest standard deviation (Hojat & Xu, 2004).
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