[R-meta] min sample size for three random variables in meta-analysis

[Michael Dewey]

Dear Jose

Unfortunately this is a plain text list and your post in HTML has got 
scrambled so as to be almost unreadable.

Just to clarify, when you say small sample size do you mean a small 
number of primary studies or that individual studies were based on small 
numbers? Is k the number of primary studies?

Michael

On 21/07/2022 15:42, Jose Valdebenito wrote:
> Hi,
> 
> I am conducting a (multi-level) meta-analysis with some sample sizes that
> are a bit small.
> 
> I was wondering if there is a kind of rule of thumb regarding minimum
> sample size number, and the maximum number of random variables I can add to
> the models.
> 
> I would like to add 3 (as suggested in Cinar et al. Methods Ecol Evol.
> 2022;13:383–95), but I am afraid that might incur in overparameterization
> if I have, say k=10?
> 
> These are the random variables:
> -Phylogenetic relatedness
> -Study ID
> -Species ID
> 
> Also, would it be any different in a meta-regression?
> 
> Here I paste the model and dataset so you can see:
> 
> m2 <- rma.mv(L_d, L_v,
>                          data = df,
>                           random = list(~1|species_2,
>                                                 ~1|study.ID,
>                                                 ~1|spp),
>                            R = list(species_2 = vcv), digits = 3)
> 
> 
>> head(df, 10)
> species_2                                 spp
>             study.ID         L_d         L_v
> Grus_americana                       Grus_americana
> p.b.4             0.000       0.135
> Loxia_leucoptera                      Loxia_leucoptera
> p.b.15          1.057        0.068
> Centrocercus_urophasianus    Centrocercus_urophasianus   p.b.60
> 0.384        0.021
> Pica_nuttalli                              Pica_nuttalli
>          p.b.8            -2.042      0.037
> Acrocephalus_paludicola          Acrocephalus_paludicola       17
>      0.000      0.068
> Acrocephalus_paludicola          Acrocephalus_paludicola       17
>        -4.978      0.334
> Lepidothrix_coronata                Lepidothrix_coronata              20
>               -2.043     0.088
> Erithacus_rubecula                   Erithacus_rubecula                35
>                -1.723      0.401
> Fringilla_coelebs                       Fringilla_coelebs
>   35                 -2.697      0.111
> Parus_caeruleus                       Parus_caeruleus                    35
>                 4.862      0.559
> 
> 
> Thanks in advance,
> Joe
> 
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> 
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-- 
Michael
http://www.dewey.myzen.co.uk/home.html