[R] replicating the odds ratio from a published study

Peter Dalgaard P.Dalgaard at biostat.ku.dk
Fri Jan 26 14:57:27 CET 2007

Michael Dewey wrote:
> At 09:04 26/01/2007, Bob Green wrote:
>> I wanted to compare odds ratio across studies and tried to replicate 
>> the results from a study but have not been able to determine how to 
>> do this in R.
>> The study reported a sample of 961 men, of whom 41 had a disorder. 
>> The reported raw odds ratio was 6.52 (4.70-9.00)
> For an odds ratio you require two odds from which you form the odds ratio.
> You only have one odds.
> Do you have another one lying around somewhere?
Alternatively, the odds ratio presumably compares two groups. If you
know the group sizes, the two odds ratios may be reconstructed. If I
make a wild guess that the groups are roughly equal, I might get

> M <- cbind(c(460,460),c(6,35))
> M
     [,1] [,2]
[1,]  460    6
[2,]  460   35
> fisher.test(M)

        Fisher's Exact Test for Count Data

data:  M
p-value = 7.406e-06
alternative hypothesis: true odds ratio is not equal to 1
95 percent confidence interval:
  2.393209 17.104976
sample estimates:
odds ratio

Judging by the c.i., the groups are probably *not* of similar size. I
suppose that the high-incidence group is a bit smaller so that the count
of advverse events is more similar. M <- cbind(c(803,117),c(21,20)) is a
bit more like it, but your (Bob's) confidence interval is narrower even
than this.

   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 35327907

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