I have gathered data from a number of studies where two different groups have performed the same task. For each group in each study, I have number of observations as well as the mean and standard deviation of the performance.
I've been comparing the difference in group means using standard meta-analytic methods, where you convert your data to a Cohen's d as well as a variance for that Cohen's d for each study. However, now I'd like to investigate whether the two groups differ in terms of their respective variances, that is, whether one group has a more narrow distribution of scores around the mean than the other.
I know there are tests of equal variance when it comes to single experiments, but I'm not aware of any meta-analytic approaches for investigation this question. Are there any?