Dear Janina

On 18/11/2016 12:04, Janina Steinert wrote:
Hi!

I am running a multi-level meta-regression in R using the metafor package.
I have specified a univariate multi-level meta-regression as follows:

Test_MR <- rma.mv(yi = effectsize_estimates, V = effsize_sd2, data = Test,
                  mods = ~ x, random = list(~ 1 | coeff, ~ 1 | study))

Can someone help explain what this code specifies exactly? Can I define
this as a mixed-effects model whereby the moderator X is a fixed effect and
random effects denote heterogeneity of effect sizes within study clusters
and between clusters?

Can someone explain what the ~1 at the end of the line specifies?

The ~ sign is part of a formula and the 1 means the intercept so you are saying you want a random intercept for each coeff and for each study. You are correct that x is the fixed effect of the moderator.

Have you looked at some of the examples on the metafor website? There is a whole range there which cover some of the issues you raise. Point your browser at http://www.metafor-project.org/ and then look for the tips and for the analyses in the navigation panel.

Thank you!

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Michael
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