Systematic reviews are a building block in Evidence Based information as they appraise and synthesise primary research, thus creating a stronger evidence base to support a given hypothesis.
The methodology used to synthesise the primary research papers varies depending on whether there is enough similarity (homogeneity) in the methodologies used in each research paper selected for the review. When there is sufficient homogeneity, the data from the primary research papers can be synthesised in a meta-analysis. Meta-analysis uses statistical methods to combine the results from the selected papers.
In cases where the primary research papers have used a variety of research methodologies (heterogeneity), a meta-synthesis can be undertaken to combine the results. Meta- synthesis interpret rather than aggregate the data in the papers.
Systematic reviews of qualitative research use meta-synthesis.