![](img013.GIF) |
The decision on what studies to
include in a meta-analysis should be based on a focused research question. Some of the
things to consider are (1) types of study designs to include (for example, randomized
trials versus randomized and nonrandomized trials), (2) types of subjects to include (for
example, gender, age, medical condition(s), etc.), (3) types of publications (for example,
published journal articles only versus published and unpublished articles), (4) language
restrictions, if any (for example, English-language articles only versus all), (5) types
of interventions (for example, aerobic exercise only versus aerobic and progressive
resistance exercise), and (6) time frame for included studies (for example, studies
conducted between January 1960 and December 2000). |