15로 계산한 결과 각 군당 31명이 필요하였으며 선행연구에서의 10%의 탈락률을 고려하여 각 군에 34명을 선정하였다.
As a result of calculating 15, 31 people were needed for each group, and 34 people were selected for each group considering the 10% dropout rate in previous studies.