This study attempted to review and compare two major meta-analytic approaches, the Hedges and Olkin approach and the Hunter and Schmidt approach, in the aspects of meta-analytic methodology. The basic methodological assumptions and characteristics between the two approaches were also discussed in terms of the analytic techniques, methodological procedures, and interpretations of the results. In addition, the two meta-analyses of the theory of planned behavior, one of the major social cognitive theories, were conducted. Based on the results, Fisher’s z-transformation, effect size estimation, heterogeneity assessment, correction for sampling error and measurement error, and confidence interval and creditability interval were discussed.