2.4. Statistical Analysis

Mann-Whitney U test was used to compare differences among groups; the difference in outcome measures within each group was assessed by the Wilcoxon Signed Ranks test. The level of significance for all statistical tests was set at p ≤ 0.05. Effect sizes were measured to determine the differences between pre-test and post-test values within the group using the formula of r = Z/√N (Z: Z-value, N: number of observations). Effect size considered small at 0.1, moderate at 0.3 and large at 0.5 [37]. Statistical analysis was conducted using SPSS statistics version 24.