[R-meta] network meta-analysis - include block (within-study) level
Juan Pablo Edwards Molina
edwardsmolina at gmail.com
Tue Aug 8 22:09:28 CEST 2017
Dear list,
I have a dataset containing crop field randomized block design experiments
with observations at plot level (experimental unit), and I want to estimate
the treatments grain yield difference relative to a untreated check.
net1 <- rma.mv(yield, vi2, mods = ~ treatment, random = ~ treatment| trial,
method="ML", struct="UN", data=df)
where yield is the vector of mean treatments yield for vi2 is the vector of
sampling variances obtained by:
vi2 <- V_yield/n (for each trial)
(V_yield = MSE from anova)
Do I need to include the block in the model? or using the experiment
treatments means will obtain the same results? I suppose something like:
net2 <- rma.mv(yield, vi2, mods = ~ treatment, random = ~ treatment| block|
trial,
method="ML", struct="UN", data=df)
If the latter would be a better approach, how do I include the sampling
variance?
Thanks in advance,
Juan Edwards
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