The last three decades the accumulation of quantitative research evidence has led to the development of systematic methods for combining information across samples of related studies. Although a few methods have been described for accumulating research evidence over time, meta-analysis is widely considered as the most appropriate statistical method for combining evidence across studies. This study reviews fixed and mixed effects models for univariate and multivariate meta-analysis. In addition, the study discusses specialized software that facilitates the statistical analysis of meta-analytic data.