Assessment of heterogeneity
We will assess statistical heterogeneity in each meta-analysis using
the T², I² and Chi² statistics. We will regard heterogeneity as
substantial if an I² is greater than 30% and either the T² is greater
than zero, or there is a low P value (less than 0.10) in the Chi² test
for heterogeneity.
Subgroup analysis and investigation of heterogeneity
If we identify substantial heterogeneity, we will investigate it using
subgroup analyses and sensitivity analyses. We will consider
whether an overall summary is meaningful, and if it is, use random-
effects analysis to produce it.
We plan to carry out the following subgroup analyses, where possible.