Re: odds ratio to chi square conversion

Posted by Kornbrot, Diana on Jun 30, 2012; 2:29pm
URL: http://spssx-discussion.165.s1.nabble.com/odds-ratio-to-chi-square-conversion-tp5713894p5713921.html

I’d be EXTREMELY dubious of including this study in a meta analysis.
The researchers are not even giving you enough information to tell whether the OR is significantly different from 1.
Here are 2 hypothetical tables with identical OR and N. chi-square and significance are materially different
 6 12  
 12 6
Chi-squ = 4.00, p = .045
   2 4  
 20 10
Chi-squ = 2.34, p = .127
Those marginals MATTER
How they can imagine that reasers would not want to know the raw odds in each group I cannot imagine!
Best
Diana

On 29/06/2012 15:58, "Rich Ulrich" <rich-ulrich@...> wrote:

No.  You need both sets of marginal totals to convert
an OR to a chi squared.  You can show this by taking a
fixed total-N and constructing various tables with the
same OR and different tests.

For the meta-analysis:  after making sure that the
information really is not there, contact the authors.
They probably will oblige.

A worthwhile meta-analysis is seldom easy.  It wants
expertise both in statistics and in the content, so, good luck.

---

Emeritus Professor Diana Kornbrot
email:  d.e.kornbrot@...    
web:    http://dianakornbrot.wordpress.com/
Work
School of Psychology
 University of Hertfordshire
 College Lane, Hatfield, Hertfordshire AL10 9AB, UK
 voice:   [phone]
   fax:     [phone]
Home
 19 Elmhurst Avenue
 London N2 0LT, UK
    voice:   [phone]
    mobile: [phone]