At 16:21 17/08/2011, Emilie MAILLARD wrote:
Hello,
Â
I would like to do a meta-analysis with the
package « metafor ». Ideally I would like to
use a mixed model because Iâm interested to
see the effect of some moderators. But the data
set I managed to collect from literature presents two limits.
Â
-Â Â Â Â Â Â Â Â Firstly, for each observation,
I have means for a treatment and for a control,
but I donât always have corresponding standard
deviations (52 of a total of 93 observations
donât have standard deviations). Nevertheless
I have the sample sizes for all observations so
I wonder if it was possible to weight
observations by sample size in the package « metafor ».
-Â Â Â Â Â Â Â Â Secondly, some observations
are probably not independent as I have sometimes
several relevant observations for a same design.
More precisely, for these cases, the control
mean is identical but treatment means varied.
Ideally, I would not like to do a weighted
average for these non-independent observations
because these observations represent levels of a
moderator. I know that the package « metaforÂ
» is not designed for the analysis of
correlated outcomes. What are the dangers of
using the package even if observations are not really independent ? Â
Emilie,
I am not sure whether this is the answer to your
problem of observations which are not independent
but you might also look at the metaSEM package
http://courses.nus.edu.sg/course/psycwlm/internet/metaSEM/
I am still trying to understand his paper on this
(see link for reference) but he is trying to
embed meta-analysis within the structural
equation framework and it may be possible to cope
with lack of independence in that way. But as I
say I am still trying to come to grips with the paper.
Â
Thank you for your help,
Â
Ãmilie.
[[alternative HTML version deleted]]
Michael Dewey
i...@aghmed.fsnet.co.uk
http://www.aghmed.fsnet.co.uk/home.html
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