[R-meta] Can/should we code for treatment groups?

[Simon Harmel]

Dear Meta-Analysis Experts,

My understanding is that when coding for any random feature in studies, the
code (numeric or otherwise) should denote the same thing across the
studies. For example, measure "A" in study 1 and study 2, 3 ... should all
refer to the same thing.

But some of my studies have multiple treatment groups (trt_grp) and I'm
simply coding them 1, 2, ... in each study. Thus, trt_grp "1" in study 1
and study 2, 3,... DON'T necessarily refer to the same thing. Same is true
for "samp" (independent samples of subjects recruited in each study) across
the studies.

So, my question is; can "trt_grp" and "samp" be used as
random-effects and be generalizable beyond their levels (or can they even
be used as fixed effects)?

I highly appreciate your input,
Simon

study samp trt_grp measure time
1       1        1          A             0
1       1        2          B            1
1       2        1          A             0
1       2        2          B            1
2       1        1          A             0
2       1        2          B            0

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