Abstract
Okumura (2007) proposed a simulation-based method of sample size determination for hierarchical linear models using posterior predictive distribution. In this article, Okumura's method is applied to a social psychological research which focuses on the difference of self-evaluation score of mathematics achievement in TIMSS 2003 between Japanese and American 8th grade students. The result says that we can keep high statistical power and can estimate the difference in high precision using a sample of about 240 students, and the size of the difference is considered to be the one that cannot be ignored from the psychometrical viewpoint.
