-----Original Message-----
From: Luke Martinez [mailto:martinezlukerm at gmail.com]
Sent: Sunday, 09 January, 2022 7:53
To: R meta
Cc: Viechtbauer, Wolfgang (SP)
Subject: Estimating "overall effect" in meta-regression
Dear R-meta Community,
I'm meta-analyzing a group of pre-post studies. My first RQ is: what
is the "overall effect" of policy X on a dependent variable.
I know that I can fit an intercept-only model to answer this RQ.
But an intercept-only model estimates the average effect size across
BOTH pre-tests (before policy X implementation) and post-tests (after
policy X implementation), while pre-test effect sizes don't contain
any policy X effect.
Given that, is it appropriate to use an intercept-only model to answer
this RQ, or I actually need to use a time indicator as a moderator to
separate the pre- from post-test effect sizes to answer this RQ (in
which case the original RQ must change too)?
Thank you for helping me better conceptualize this basic question,
Luke