Meta-analyses are becoming increasingly popular in the field of health and risk communication—meta-analyses allow for more precise estimations of the magnitude of effects and the robustness of those effects across empirical studies in a particular domain. Despite its popularity, most scholars are not trained in the basic methods involved with meta-analyses. There are advantages to meta-analysis in comparison to other forms of research synthesis. An overview of the methods involved in conducting and reporting meta-analytical research is helpful.
However, the methods involved with meta-analyses are not as clear-cut as they may first appear. Numerous issues must be considered and various arbitrary decisions are required during the process. These issues and decisions relate to various topics such as inclusion criteria, the selection of sources, quality assessments for eligible studies, and publication bias. Basic knowledge of these issues and decisions is important for interpreting the outcomes of a meta-analysis correctly.
Article
Meta-Analysis in Health and Risk Messaging
Simon Zebregs and Gert-Jan de Bruijn
Article
Systematic Reviews and Meta-Analyses of Crime Prevention Evaluations
Anthony Petrosino, Claire Morgan, and Trevor Fronius
Systematic reviews and meta-analyses have become a focal point of evidence-based policy in criminology. Systematic reviews use explicit and transparent processes to identify, retrieve, code, analyze, and report on existing research studies bearing on a question of policy or practice. Meta-analysis can combine the results from the most rigorous evaluations identified in a systematic review to provide policymakers with the best evidence on what works for a variety of interventions relevant to reducing crime and making the justice system fairer and more effective. The steps of a systematic review using meta-analysis include specifying the topic area, developing management procedures, specifying the search strategy, developing eligibility criteria, extracting data from the studies, computing effect sizes, developing an analysis strategy, and interpreting and reporting the results.
In a systematic review using meta-analysis, after identifying and coding eligible studies, the researchers create a measure of effect size for each experimental versus control contrast of interest in the study. Most commonly, reviewers do this by standardizing the difference between scores of the experimental and control groups, placing outcomes that are conceptually similar but measured differently (e.g., such as re-arrest or reconviction) on the same common scale or metric. Though these are different indices, they do measure a program’s effect on some construct (e.g., criminality). These effect sizes are usually averaged across all similar studies to provide a summary of program impact. The effect sizes also represent the dependent variable in the meta-analysis, and more advanced syntheses explore the role of potential moderating variables, such as sample size or other characteristics related to effect size.
When done well and with full integrity, a systematic review using meta-analysis can provide the most comprehensive assessment of the available evaluative literature addressing the research question, as well as the most reliable statement about what works. Drawing from a larger body of research increases statistical power by reducing standard error; individual studies often use small sample sizes, which can result in large margins of error. In addition, conducting meta-analysis can be faster and less resource-intensive than replicating experimental studies. Using meta-analysis instead of relying on an individual program evaluation can help ensure that policy is guided by the totality of evidence, drawing upon a solid basis for generalizing outcomes.
Article
Meta-ethnography in Education
George W. Noblit
Meta-ethnography is a very popular method for the synthesis of qualitative research. It was designed for the field of education but has been exceedingly popular in the health sciences. In education, slow growth has given way to almost furious development. Meta-ethnography is a method for synthesizing qualitative studies. Studies are identified as related to a phenomenon of interest and these are reviewed and read repeatedly, leading to both a reduction in the number of relevant studies and further specification of the phenomenon of interest. The synthesis is a translation of the complete interpretive storylines of each study into the others. There are three types of translation: reciprocal (the storylines are commensurate and reinforce each other), refutational (the storylines critique each other), and line of argument. Each study contributes something distinct to a new storyline that characterizes all the studies taken together. Effecting these translations remains a challenge for most who conduct meta-ethnographies. The work in the 21st century in education has established meta-ethnography as an interpretive and critical endeavor, moving well beyond the original proposal.
