[R-meta] question regarding metafor and OR
Viechtbauer Wolfgang (SP)
wolfgang.viechtbauer at maastrichtuniversity.nl
Wed Sep 27 23:10:14 CEST 2017
Dear Sandro,
I assume you mean that you have fitted a model with *log odds ratios* and now you want to fit a model directly to the odds ratios.
Why would you want to fit a model to the odds ratios? Odds ratios are not symmetric around 1, so results are going to be non-sensical (the average of OR = 2.0 and OR = 0.5 is not 1 but 1.25, so even though the two odds ratios are exact opposites of each other, their average yields a value above 1). Also, odds ratios do not have a normal sampling distribution (not even approximately), so model assumptions are therefore violated.
Best,
Wolfgang
-----Original Message-----
From: R-sig-meta-analysis [mailto:r-sig-meta-analysis-bounces at r-project.org] On Behalf Of Sandro Marini
Sent: Wednesday, 27 September, 2017 17:54
To: r-sig-meta-analysis at r-project.org
Subject: [R-meta] question regarding metafor and OR
I have a model with Odds Ratio and their 95%, I have also the estimates and
their standard errors
So far I have used the estimates = *yi *and the standar errors = *sei *in
the *rma* function.
But what if I wanted to use the Odds Ratio? how I should define the *vi* or
the *sei* arguments in the same *rma* function?
Thank you for your help,
Sandro
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