[R-meta] unsigned effect sizes

[James Pustejovsky]

Hi meta-analysis folks,

I have a kind of vague question about something I've run across a few
times. There are some (perhaps rare) situations where investigators are
interested in the absolute magnitude of an effect but where the sign or
direction of the effect is arbitrary or not meaningful. Consequently,
meta-analysts of such effects might like to work with _unsigned_ effect
size estimates rather than the estimates that describe both magnitude and
direction. However, taking the absolute value of an estimate changes its
sampling distribution--potentially quite drastically!--in a way that would
make conventional meta-analytic models
(fixed/common/random/multi-level/multi-variate) perform rather poorly.

Does anyone know of work on methods for synthesis of unsigned effects, that
actually account for the consequences of using absolute effect size
estimates?

James

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