Evidence-Based Medicine

W
Weighted mean difference (WMD)
A measure of effect size used when outcomes are continuous (such as symptom
scores or height) rather than dichotomous (such as death or myocardial
infarction). The mean differences in outcome between the groups being studied
are weighted to account for different sample sizes and differing precision
between studies. The WMD is an absolute figure and so takes the units of the
original outcome measure.
A continuous outcome measure, similar to standardised mean differences but
based on one scale so in the real units of that scale. Ideal ly should be replaced
by a discrete outcome and a relative risk; however, we use WMD if this is not
possible.
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