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[R-meta] Random Effect for Continuous Moderator in Three-Level Meta-Analysis

Wolfgang Viechtbauer 
Hi Andrew,

Yes, this is possible if you install the 'devel' version of metafor. It includes an as-of-yet undocumented 'struct' option, namely "GEN". This allows for random effects terms, such as:

~ x1 + x2 + ... | factor

where x1, x2, and so on can be continuous (but also categorical) variables. So, for the example you used, it would be:

m2.ml <- rma.mv(yi, vi,
                random = ~ I(year-1990.591)| district, struct="GEN",
                method="ML",
                digits = 3,
                data=dat.konstantopoulos2011)

BUT:

1) Unless you want to assume that the average slope is 0, one should also include the same predictor as a fixed effect:

m2.ml <- rma.mv(yi, vi, mods = ~ I(year-1990.591),
                random = ~ I(year-1990.591)| district, struct="GEN",
                method="ML",
                digits = 3,
                data=dat.konstantopoulos2011)

2) 'year' is actually constant within districts, so the use of random slopes for this predictor doesn't make much sense.

Note: The "GEN" structure is undocumented, which implies that this feature is really still in the testing phase.

Best,
Wolfgang

Thread (3 messages)

Andrew Loignon Random Effect for Continuous Moderator in Three-Level Meta-Analysis Jan 10 Wolfgang Viechtbauer Random Effect for Continuous Moderator in Three-Level Meta-Analysis Jan 10 Andrew Loignon Random Effect for Continuous Moderator in Three-Level Meta-Analysis Jan 11