There are various types of reviews. The most authoritative review, i.e. the review that presents the most valid and reliable scientific evidence, is the systematic review. The aim of a systematic review (SR) is to identify all relevant studies on a specific topic as comprehensively as possible, and to select appropriate studies based on explicit criteria. These studies are then assessed to ascertain their internal validity. A systematic approach is applied to selecting studies: the methodological quality of the studies in question is assessed by several researchers independently of each other on the basis of explicit criteria. A SR is therefore transparent, verifiable and reproducible. Because of this the likelihood of bias is considerably smaller in a SR compared to traditional literature reviews.
A Rapid Evidence Assessments (REAs) is another type of evidence summary that can inform practice. An REA applies the same methodology as a SR and both involve the following steps:
3. Inclusion Criteria
4. Search Strategy
5. Study Selection
6. Data Extraction
7. Critical Appraisal
8.2. Causal Mechanism
8.3. Main Findings
8.4. Moderators and Mediators
12. Implications for Practice
The main way in which these two types of summaries vary is in relation to the time and resources used to produce them and the scope and depth of the results produced. In order to be ‘rapid’ an REA makes concessions in relation to the breadth, depth and comprehensiveness of the search. Aspects of the search may be limited to produce a quicker result:
· Searching: consulting a limited number of databases, and excluding unpublished research.
· Inclusion: only including specific research designs (e.g. meta-analyses or controlled studies)
· Data Extraction: only extracting a limited amount of key data, such as year, population, sector, study desig, sample size, moderators/mediators, main findings, and effect sizes.
· Critical Appraisal: limiting quality appraisal to methodological appropriateness and quality.
Due to these limitations, an REA may be more prone to bias than a SR. A SR, however, usually takes a team of academics several months (sometimes even more than a year) to produce – as it aims to identify all published and unpublished relevant studies – whereas an REA might take two skilled persons only several weeks. In general, an organization will not have time or financial means to hire a team of academics to conduct a SR on a managerial topic of interest. As a result, an REA is the most widely used method of reviewing the scientific literature within Evidence-Based Management.