[R-meta] specification of phi in vcalc

[Danielle Hiam]

Hello,

I am running a meta-analysis that has nested data and dependent effect sizes (multiple timepoints). Therefore, I need to take into account effect sizes that are correlated and also cluster within studies. I will run vcalc, then the rma.mv function and then use robust with clubsandwich set to true to "correct" for any mis-specification of the model. However, I am looking for some clarification regarding how to "guess" the value for phi in the vcalc function, R code: V <- vcalc(FC_SD, cluster, time1=Time_NUM, data, phi=0.6).

When I change phi from 0.6 to 0.8 in vcalc I get very different results from the meta-analysis (rma.mv followed by robust(.... Clubsanwich=T). I have read James Pustejovsky paper (DOI: https://doi.org/10.1007/s11121-021-01246-3) on this, where he suggests that in situations where no information is available, the meta-analyst might pick a plausible value and then conduct sensitivity analysis across a range reasonable values. How would I go about this?

Any information regarding specification of phi would be greatly appreciated

Thanks,
Danielle

Deakin University
Melbourne Burwood Campus, 221 Burwood Highway, Burwood VIC 3125
danielle.hiam using deakin.edu.au
ipan.deakin.edu.au
Deakin University CRICOS Provider Code: 00113B

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