[R-meta] Dear Wolfgang

[Viechtbauer, Wolfgang (SP)]

Dear Juhyung,

Briefly, I am not aware of any proper evidence based guidelines for such a threshold. You sometimes see people mention that there should be 5 or 10 studies per moderator, but these are just heuristics. One could do a proper power analysis if one is worried about false negatives. See

https://www.jepusto.com/publication/power-approximations-for-dependent-effects/

for some recent work that might be applicable to your case (since your post implies that you are dealing with a more complex data structure).

Best,
Wolfgang

>-----Original Message-----
>From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces using r-project.org] On
>Behalf Of Lee, Ju
>Sent: Wednesday, 26 January, 2022 23:07
>To: r-sig-meta-analysis using r-project.org
>Subject: [R-meta] Dear Wolfgang
>
>Hello,
>
>I am currently using a mixed effect meta-regression to explore the effects of
>different environmental variables on fish densities in coastal habitats.
>For this, I am constructing a different model for individual fish species, in
>which my goal is to identify important predictor variables separately for each
>species by using aicc-based model selection (glmulti).
>For each fish dataset, I usually identify 3-4 potentially important predictor
>variables – which include both categorical and continuous variables – based on a
>priori hypothesis and the statistical test of omnibus test (of each individual
>predictor variable).
>I am only testing the main effects and not the interaction of multiple variables
>being included in the final models.
>
>The problem I am running into is the small number of studies being available for
>many species, with the number of study response (effect size, not independent
>study) ranging from 6 to 100 for different fish species.
>
>So my question is:
>
>Is there a commonly used threshold for the multiple meta-regression using rma.mv
>to be reliable and avoid false positive or negative relationship?
>From
>https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0229345&ty
>pe=printable I read that, for meta-regression, n should be greater than 8 for low
>variance data, but should be greater than 25 for high variance data.
>I wanted to seek your advice on what would be a good threshold criteria for
>minimum study response (effect size) number for running the meta-regression
>models.
>Also, could we also apply similar threshold for number of independent studies
>(not effect size, but the actual publication) included in each dataset as well?
>
>Thank you.
>Sincerely,
>Juhyung
>
>Juhyung Lee
>Postdoctoral Fellow
>Marine Science Center, Northeastern University
>430 Nahant Rd, Nahant, MA 01908, USA
>Phone: +1(650)285-7614