<P> Systematic reviews often, but not always, use statistical techniques (meta - analysis) to combine results of eligible studies, or at least use scoring of the levels of evidence depending on the methodology used . An additional rater may be consulted to resolve any scoring differences between raters . Systematic review is often applied in the biomedical or healthcare context, but it can be applied in any field of research . Groups like the Campbell Collaboration are promoting the use of systematic reviews in policy - making beyond just healthcare . </P> <P> A systematic review uses an objective and transparent approach for research synthesis, with the aim of minimizing bias . While many systematic reviews are based on an explicit quantitative meta - analysis of available data, there are also qualitative reviews which adhere to standards for gathering, analyzing and reporting evidence . The EPPI - Centre has been influential in developing methods for combining both qualitative and quantitative research in systematic reviews . The PRISMA statement suggests a standardized way to ensure a transparent and complete reporting of systematic reviews, and is now required for this kind of research by more than 170 medical journals worldwide . </P> <P> Recent developments in systematic reviews include realist reviews, and the meta - narrative approach . These approaches try to overcome the problems of methodological and epistemological heterogeneity in the diverse literatures existing on some subjects . </P> <P> The main stages of a systematic review are: </P>

Which of the following best describes the primary function of the literature review