Saturday, July 2, 2016

New Article by Gene Glass on the Limits of Meta-analysis in Education

Gene glass is one of education's most accomplished and perceptive quantitative methodologist. He is the developer of meta-analysis, the statistical method for consolidating the findings of related studies into a single result.

In a recent article in the journal Educational Researcher*, Dr. Glass notes the following interesting conclusions about meta-analysis.

  • Meta-analysis is unique in that it is possibly the only education born widely-used quantitative methodological tool that has been adopted by medical research. Typically education research seeks to emulate what medical research is doing to gain credibility as a science. In this case, medical research adopted this education methodology and now uses it to an even greater extent then education.
  • Meta-analysis has not produced incontrovertible findings that can lead to education policy.

While the first conclusion is interesting and a coup for education research, the second is a bombshell.  It is rare that the inventor of something points out its limitation after an extended period of use. The problem is that unlike medical research where related studies/drug trials tend to find similar effects, in education the variability of findings within a given meta-analysis is usually much larger than the overall effect. This is yet another problem with relying on small effect sizes in education to drive policy and conclusions that something is effective.

While the existence of large variation within a given meta-analysis is problematic, it also represents an opportunity. One can look inside the accompanying table that lists the characteristics of all the studies in the meta-analysis to identify those studies with the biggest effect sizes and then look at them to see if there are any useful common characteristics. That is the gist of the the section "How to Review a Meta-Analysis" in Chapter 3 of the text. Of course, it may be that the studies with the highest Effect Sizes are at the early elementary grades, or very short term interventions using a measure developed by the researcher, which will be of little help if you are trying to raise the scores of a middle or high school on more standardized measures. However, you never know whether the results can help improve your practice till you look into the most promising studies.

* Glass, G. V. (2016). One Hundred Years of Research Prudent Aspirations. Educational Researcher, 45(2), 69-72.

No comments:

Post a Comment