Sampling method
To reduce a type II error and increase the power, a preliminary power analysis using G*power 3.1.9.7 computer program, based on the test family: t-tests, statistical test: means: Wilcoxon-Mann-Whitney test (two groups); power (1 − β)  =  0.85; α  =  0.05; effect size  =  0.5 were used to calculate the sample size. It indicated that a total sample of 108 people would be needed [