Statalist


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: st: Stata not recommended for exact 2x2 test


From   "Kieran McCaul" <kamccaul@meddent.uwa.edu.au>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Stata not recommended for exact 2x2 test
Date   Tue, 11 Nov 2008 02:49:39 +0900

"Did Prof. Ludbrook (or anybody) indicate what algorithms Testimate 6.0
uses
for exact tests of odds ratio = 1, relative risk = 1 and risk difference
= 0
in the randomized clincial trial (single-conditioned) situation?"


The short answer is no.  Quote from Ludbrook (2008): "The algorithms
that the software packages use for the various exact tests are not
usually made explicit, so I have had to infer them from the outcome of
the tests."

But it appears that they are based on a test proposed by Barnard:
Barnard GA. A new test for 2x2 tables. Nature 1945;156:177.


______________________________________________
Kieran McCaul MPH PhD
WA Centre for Health & Ageing (M573)
University of Western Australia
Level 6, Ainslie House
48 Murray St
Perth 6000
Phone: (08) 9224-2140
Fax: (08) 9224 8009
email: kamccaul@meddent.uwa.edu.au
http://myprofile.cos.com/mccaul 
_______________________________________________
The fact that no one understands you doesn't make you an artist.

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Joseph
Coveney
Sent: Tuesday, 11 November 2008 12:48 AM
To: Statalist
Subject: Re: st: Stata not recommended for exact 2x2 test

David Airey  wrote:

I was looking at the following citation, and found the author
explicitly argued against using Stata for a particular 2x2 exact test.

[snip]
[Quote from article:] (ii) Comparative trials (singly conditioned).
These correspond to the usual experimental design in biomedical work, in
which a sample of convenience is randomized into two treatment groups,
so
that the group (column) totals are fixed in advance. The proper tests of
significance are exact tests on the odds ratio, on the ratio of
proportions
(relative risk and risk ratio) or on the difference between proportions.
[snip]                       . . . for an exact test on OR=1,
it is safe only to use the Testimate single-conditioned
option. For the exact test on RR=1, and for the exact
test on the difference in proportions (p2 - p1=0), it is
safe to use StatXact and Testimate, but not Stata.

------------------------------------------------------------------------
--------

David,

Did Prof. Ludbrook (or anybody) indicate what algorithms Testimate 6.0
uses
for exact tests of odds ratio = 1, relative risk = 1 and risk difference
= 0
in the randomized clincial trial (single-conditioned) situation?

Joseph Coveney


*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index