Methodology
Design : Simple randomized sampling
Setting : The secondary school students and collage in Nakhonratchasima
Sample size : Power Analysis Parameters (Cohen,1988):
Probability of a type one error of .05
Expected Sample Size: (N=128) n = 64 / gr. for F test on two means with equal sample size in the ANCOVA
Final sample size: N= 104 (Ex = 53, Con = 51)