The sample size was determined via use of
the ANOVA power table, for three groups, with a
significance level of 0.05 and power of 0.80.24
Since no similar study had been conducted in
Thailand, an effect size of 0.20 was chosen. Thus, a
minimum of 14 subjects per group was determined
to be needed. However, it appeared the estimated
number of subjects was too small to demonstrate
normal distribution of the variable scores and deal
with possible subject attrition. Since there were 246
potential subjects available, the PI planned to have at least 50 participants in each group.