9.4.1  Meta-analysis

An important step in a systematic review is the thoughtful consideration of whether it is appropriate to combine the numerical results of all, or perhaps some, of the studies. Such a meta-analysis yields an overall statistic (together with its confidence interval) that summarizes the effectiveness of the experimental intervention compared with a control intervention (see Section 9.1.2). This section describes the principles and methods used to carry out a meta-analysis for the main types of data encountered.


Formulae for all the methods described are provided in a supplementary document, Statistical algorithms in Review Manager 5 (available on the Handbook web site), and a longer discussion of the issues discussed in this section appears in Deeks et al. (Deeks 2001).