At 22:01 26/01/2007, Peter Dalgaard wrote: >Bob Green wrote: >>Peetr & Michael, >> >>I now see my description may have confused the issue. I do want to >>compare odds ratios across studies - in the sense that I want to >>create a table with the respective odds ratio for each study. I do >>not need to statistically test two sets of odds ratios. >> >>What I want to do is ensure the method I use to compute an odds >>ratio is accurate and intended to check my method against published sources. >> >>The paper I selected by Schanda et al (2004). Homicide and major >>mental disorders. Acta Psychiatr Scand, 11:98-107 reports a total >>sample of 1087. Odds ratios are reported separately for men and >>women. There were 961 men all of whom were convicted of homicide. >>Of these 961 men, 41 were diagnosed with schizophrenia. The >>unadjusted odds ratio is for this group of 41 is cited as >>6.52 (4.70-9.00). They also report the general population aged >>over 15 with schizophrenia =20,109 and the total population =2,957,239.
Looking at the paper (which is in volume 110 by the way) suggests that Peter's reading of the situation is correct and that is what the authors have done. >>Any further clarification is much appreciated, >> >> >A fisher.test on the following matrix seems about right: > > matrix(c(41,920,20109-41,2957239-20109-920),2) > > [,1] [,2] >[1,] 41 20068 >[2,] 920 2936210 > > > fisher.test(matrix(c(41,920,20109-41,2957239-20109-920),2)) > > Fisher's Exact Test for Count Data > >data: matrix(c(41, 920, 20109 - 41, 2957239 - 20109 - 920), 2) >p-value < 2.2e-16 >alternative hypothesis: true odds ratio is not equal to 1 >95 percent confidence interval: >4.645663 8.918425 >sample estimates: >odds ratio > 6.520379 > >The c.i. is not precisely the same as your source. This could be >down to a different approximation (R's is based on the noncentral >hypergeometric distribution), but the classical asymptotic formula gives > > > exp(log(41*2936210/920/20068)+qnorm(c(.025,.975))*sqrt(sum(1/M))) >[1] 4.767384 8.918216 > >which is closer, but still a bit narrower. > Michael Dewey http://www.aghmed.fsnet.co.uk ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
