Subgroup analyses allow to examining the influence of a categorical moderator on the effect magnitude in meta-analysis. We conducted a simulation study using a dichotomous moderator, and compared the impact of pooled versus separate estimates of the residual between-studies variance on the statistical performance of the QB(P) and QB(S) tests for subgroup analyses assuming a mixed-effects model. Our results suggested that a similar performance can be expected as long as there are at least 20 studies and these are approximately balanced across categories. Conversely, when subgroups were unbalanced, the practical consequences of having heterogeneous residual between-studies variances were more evident, with both tests leading to the wrong statistical conclusion more often than in the conditions with balanced subgroups. A pooled estimate should be preferred for most scenarios, unless the residual between-studies variances are clearly different and there are enough studies in each category to get precise separate estimates.
|Number of pages||18|
|Journal||British Journal of Mathematical and Statistical Psychology|
|Early online date||6 Feb 2017|
|Publication status||Published - Nov 2017|
- mixed-effects model
- subgroup analysis
- between-studies variance