[R-meta] network meta-analysis - include block (within-study) level
Pretty close to that structure ?you say?: I have ?several treatments at each block (balanced experiments), actually different set of treatments across the k-trials (all trials have the untreated Check) This are a few lines of trial 3: ? trt trial bk x y Check 3 1 40 2493 Check 3 2 45 2173 Check 3 3 40 2628 Check 3 4 40 2168 Fox 3 1 35 3194 Fox 3 2 30 2363 Fox 3 3 35 2887 Fox 3 4 30 3278 NTX 3 1 40 2988 NTX 3 2 35 2361 NTX 3 3 35 2341 NTX 3 4 35 3218 ? |? Also, do you have the raw mean and variance (or SD) and sample size for each row of the dataset? It seems like you are first fitting some kind of ANOVA within each study, but | that might actually complicate things. Yes, I have the raw full dataset so I ?have the observation level ?values to calculate SD, means..? Several authors from the Phytopathology area use ANOVA MSE : "...The within-study variance (V) for IND or DON for these fungicide trials is the residual variance (mean square error) from an analysis of variance (ANOVA) of the effects of treatment on disease or toxin. Where the original data were available, this variance was calculated directly from an ANOVA..." http://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO-97-2-0211 *Juan* On Tue, Aug 8, 2017 at 6:03 PM, Viechtbauer Wolfgang (SP) <
wolfgang.viechtbauer at maastrichtuniversity.nl> wrote:
Dear Juan,
Could you show a bit of the data (structure)? In particular, does each
block contain two treatments, so that the structure looks something like
this?
trial block treatment mean
--------------------------
1 1 1 ...
1 1 2 ...
1 2 1 ...
1 2 2 ...
2 1 1 ...
2 1 2 ...
2 2 1 ...
2 2 2 ...
2 3 1 ...
2 3 2 ...
...
??
Also, do you have the raw mean and variance (or SD) and sample size for
each row of the dataset? It seems like you are first fitting some kind of
ANOVA within each study, but that might actually complicate things.
Best,
Wolfgang
-----Original Message-----
From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-
bounces at r-project.org] On Behalf Of Juan Pablo Edwards Molina
Sent: Tuesday, August 08, 2017 22:09
To: r-sig-meta-analysis at r-project.org
Subject: [R-meta] network meta-analysis - include block (within-study)
level
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