Effect Size Estimation in Meta-Analysis

As the rate of growth of the literature in education has grown exponentially, it has become recognized that methods of integrating like studies mathematically are needed. Meta-analysis is one technique which has been developed to fulfill this need. For the application of meta-analysis, it is important that as many studies as possible be included. Methods for estimating effect sizes when complete data are not reported are presented. When not precise, these methods provide a conservative estimate and, therefore, allow for the inclusion in a meta-analysis of relevant studies whose data might otherwise be discarded.