P.Mean: My very first meta-analysis (created 2008-07-23).
I am a research student embarking upon a systematic review and possible metanalysis. I am currently in the process of developing a protocol. I have been having difficulty understanding the statistical issues especially since I am not very good at mathematics. Could you kindly refer me to a source that would help me understand in a step by step way the concepts needed in doing a meta analysis? For example heterogeneity and the tests used for it which one is preferred and when; when to use subgroup analysis and when to use metaregression. I have been reading the Cochrane hand book for the purpose as advised by my supervisor but have not been able to understand the concepts. Any help from you would be greatly appreciated.
Meta-analysis is not for amateurs. Here is some general guidance, but please don't consider it a substitute for a consultation with someone who has formal experience in this area.
1. Write a protocol that is at least as detailed as the protocols that were written for the individual studies that you are combining.
2. Get two people to independently apply the inclusion and exclusion criteria. Get them to independently abstract information from the journals. Measure the degree of agreement among the two evaluators.
3. Assess heterogeneity qualitatively rather than quantitatively. Formal tests and measures of heterogeneity have an uncertain endorsement in the research community. Besides, in your first meta-analysis, why add more complicated mathematics?
4. A thorough search for articles prior to the meta-analysis is far better than trying to assess and adjust for publication-bias after all the data is in. Funnel plots look pretty, but it is unclear if they really help.
5. I would minimize both the subgroup analysis and the meta-regression. This is your first meta-analysis, so your goal is to get a passing grade, not to ace the exam. If you had to do either, use the subgroup analysis. I like meta-regression, but I would not do it on my first meta-analysis. The nice thing about subgroup analysis is that you already know how to do it.
6. Don't neglect the science/medicine. There's a famous quote "the glitter of the t-table distracts from the inadequacy of the fare." Don't get so focused on the statistical methods that you lose sight of the practical scientific/medical questions that you are interested in..
This work is licensed under a Creative Commons Attribution 3.0 United States License. This page was written by Steve Simon and was last modified on 2010-04-01. Need more information? I have a page with general help resources. You can also browse for pages similar to this one at Category: Systematic overviews.