Meta-analysis is a frequently used statistical technique which uses to combine data from several studies to evaluate the effectiveness of treatment interventions. By combining results from independent studies, we can both increase power of the study (over individual studies) and improve estimates of the size of the effect. The processes of conducting meta-analysis include developing a protocol, selecting articles, developing inclusion criteria, collecting data, data analysis and interpreting results. A major limitation of the meta-analysis is that only relevant studies which have retrievable data can be included for analysis. This causes concern for publication bias. It is obvious that metaanalysis is a useful scientific method that can pro...