Fig. 3. To know the differences of height within subject as students grow up, RMANOVA is available and the sphericity assumption should be guaranteed. To compare within subject factor which means the differences between each grades, paired comparisons between the grades could be done with adjustment of significance level like the Bonferroni's correction. To compare the between subject factor at each grade, paired comparisons could be done with significance levels adjusted by like the Bonferroni's procedure.