Saturday, 20 August 2016

Meta-analysis write up versus the literature review

My students get a bit confused between literature reviews and  meta-analyses.

A literature review is a "Detailed and justified analysis and commentary of the merits and faults of the literature within a chosen area, which demonstrates familiarity with what is already known about your research topic" (Saunders, Lewis, & Thornhill, 2007, p. 595), "to uncover new insights on a topic by reviewing the literature in a systematic way" (Aveyard, 2007, p. 18).

Meta-analysis has its roots in medicine, and is generally empirical in nature. Crombie and Davies outline it by first exploring systematic review: 
"Systematic review methodology is at the heart of meta-analysis. This stresses the need to take great care to find all the relevant studies (published and unpublished), and to assess the methodological quality of the design and execution of each study. The objective of systematic reviews is to present a balanced and impartial summary of the existing research, enabling decisions on effectiveness to be based on all relevant studies of adequate quality. Frequently, such systematic reviews provide a quantitative (statistical) estimate of net benefit aggregated over all the included studies. Such an approach is termed meta-analysis" (2009, p. 2).
Further, The Himmelfarb Health Sciences Library (2011) proposed it is:
"A subset of systematic reviews; a method for systematically combining pertinent qualitative and quantitative study data from several selected studies to develop a single conclusion that has greater statistical power. This conclusion is statistically stronger than the analysis of any single study, due to increased numbers of subjects, greater diversity among subjects, or accumulated effects and results."
Dr Heather Gray posed an interesting question on the LinkedIn Higher Education Teaching and Learning group recently: "A meta analysis of the literature or a literature review. What is the difference? What do you prefer for your PhD candidates?".

While many posters did not realise the difference in approach between the two methods, there was a general consensus that (a) a literature review was the most useful for a PhD thesis: the 'normal' approach, and (b) a meta-analysis was a lot more work, so a method better left for post-doctoral researchers.

Elton J. Crim preferred the "literature review albeit a robust one which demonstrates [students'] ability to synthesize. A meta analysis is a great skill and project for a paper or book. Most likely undertaken either with their professor/advisor or later in their career".

However, we need to be aware that the literature itself will shape the method. While Vishwanath Baba would normally "ask for a traditional literature review of my doctoral students in preparation of the thesis. I encourage a meta-analysis if a specific relationship is hypothesized and there is some ambiguity in the empirical literature about the relationship. I encourage it further if it is going to lead to some theorizing about the relationship among the variables."

Jennifer Gerow further defined the difference between the two approaches: "Traditional, narrative literature reviews are important because they should capture all the relevant literature (not just empirical studies from the meta-analysis), but they may be limited by human information processing since it is difficult to address conflicting findings across many studies (Hunter and Schmidt 2004)", whereas "A meta-analysis is a statistical technique for systematically combining the results from empirical studies on the same construct/topic (Gerow et al. 2014; Glass 1981; Hunter and Schmidt 2004; Lipsey and Wilson 2001)."

I think that clarifies things nicely :-) 



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