[R-meta] Meta-analysis with missing data
Viechtbauer, Wolfgang (SP)
wo||g@ng@v|echtb@uer @end|ng |rom m@@@tr|chtun|ver@|ty@n|
Fri Mar 29 15:16:01 CET 2019
If the outcome measure is a response ratio (log ratio of means), then one approach we have used before is to look at the studies that do report both means and SDs and see what the (average or median) coefficient of variation is in those studies. For the studies that do not report SDs, we then imputed the sampling variances using this value. See:
Hoeksema, J. D., Bever, J. D., Chakraborty, S., Chaudhary, V. B., Gardes, M., Gehring, C. A., Hart, M. M., Housworth, E. A., Kaonongbua, W., Klironomos, J. N., Lajeunesse, M. J., Meadow, J., Milligan, B. G., Piculell, B. J., Pringle, A., Rúa, M. A., Umbanhowar, J., Viechtbauer, W., Wang, Y.-W., Wilson, G. W. T., & Zee, P. C. (2018). Evolutionary history of plant hosts and fungal symbionts predicts the strength of mycorrhizal mutualism. Communications Biology, 1(1), 116.
One can also do quite fancy modeling to deal with this issue:
Also relevant in this context is:
Furukawa, T. A., Barbui, C., Cipriani, A., Brambilla, P., & Watanabe, N. (2006). Imputing missing standard deviations in meta-analyses can provide accurate results. Journal of Clinical Epidemiology, 59(1), 7-10.
From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces using r-project.org] On Behalf Of Gabriele Midolo
Sent: Friday, 29 March, 2019 15:03
To: Mekides Gardi
Cc: r-sig-meta-analysis using r-project.org
Subject: Re: [R-meta] Meta-analysis with missing data
I think this is a common issue in agricultural and ecological
meta-analyses. But I am not sure the solution to your problem depends on
metafor. However, based on my experience, there are few options to be
considered (with the following order): 1) to contact the authors of the
primary studies and ask them to provide the SD of the means; 2) to compute
the missing SD via the ‘impute_SD’ function of the R package metagear
(Lajeunesse, 2016), in case few values are missing; 3) you might consider
to perform an "unweighed meta-analysis" including also the studies without
SD to compare results with a meta-analysis including studies with available
SD only? See an example in e.g. of Humbert et al. 2016 Global Change
Biology, 22(1), 110-120. (Figure 1).
Hope this helps,
Il gio 28 mar 2019, 16:06 Mekides Gardi <mekides.gardi using uni-hohenheim.de> ha
> Dear All,
> Seeking help on meta-analysis. I am conducting a meta-analysis on the
> response of two cereal crops to elevated CO2. Most of the studies
> didn't report SD or SE. I have the mean values for both the control
> and experimental group and sample size as well.
> I read on literature there is still a way to do meta-analysis without
> SD or SE. Could you provide me with guides on how to do it in R with
> metafor package?
> Thanks in advance.
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