"...a systematic review is a scientific investigation in itself, with a pre-planned methods section and an assembly of original studies as their ‘subjects’. The results of multiple primary investigations are synthesized by using strategies that limit bias and random error. These strategies include a comprehensive search of all potentially relevant articles and the use of explicit, reproducible criteria in the selection of studies for review. Primary research designs and study characteristics are appraised, data are synthesized, and results are interpreted..."
Systematic reviews are described as "...papers that summarize other papers" and "overviews of primary studies that have used explicit and reproducible methods". Cook et al describe them thusly: "...systematic reviews are scientific investigations in themselves, with pre-planned methods and an assembly of original studies as their “subjects.”" SRs synthesize findings from key, high-powered trials and reports of therapies and interventions using explicit inclusion and exclusion criteria, and may or may not include a meta-analysis. As an approach to gathering, analyzing and synthesizing a body of research, SRs are very popular. SRs include clearly-defined protocols and procedures that ensure accountability and transparency and are typically collaborative in nature. Research teams work in conjunction with a group of professionals, experts and practitioners in the field to ensure that all key resources are located and evaluated. SRs are comprehensive in the way they capture relevant literature yet they often very specific. A set of criteria clearly defines which studies are to be included or excluded in the review - called "inclusion - exclusion" criteria. In the final analysis and synthesis, SRs are evaluated based on methodological rigour and a meta-analysis is conducted when possible.