[R-meta] Random slopes in rma.mv

Francisco Tapia Fr@nc|@co@n|ne| @end|ng |rom hotm@||@com
Thu May 20 18:28:58 CEST 2021

Dear metanalysis community:

A couple of days ago, Wolfgang provided me the information to add random slopes to rma.mv, from the metafor package (https://stats.stackexchange.com/questions/524144/random-slopes-in-rma-mv)

By changing the struct to �GEN�, I can now add random to my multilevel model. As the documentation is not up yet, I wanted to check some things regarding syntaxis of the code and the logic behind it:

  1.  If I have ID1 nested within ID2, my structure of random effects would be: ( ~ 1 | ID2/ID1) for random intercepts.  If I want to add random slopes to ID2, �Should I do it in another random effect? For example, If I add random slopes to ( ~ 1 | ID2/ID1), therefore -> ( ~ X | ID2/ID1), I�ll be adding random slopes for each level of ID1 within ID2, and for ID2 as well. �Should I leave ( ~ 1 | ID2/ID1) alone and create another random effect to add random slopes just for ID2?
  2.  If I create another random effect to add random slopes to ID2, for example, (~ X | ID2), �Would I be adding another random intercept for ID2? If so, �How, an unnecessary intercept, can affect my model? I cannot see it very clearly
  3.  If I have a crossed random effect at the same level as ID2, let�s say (~ 1 | ID3) for random intercepts. �Can both of them, ID2 and ID3, have different random slopes structure from each other, despite being in the same level?

Thanks in advance!

Francisco Tapia

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