Date:         Thu, 23 Jun 2005 10:18:00 -0700
Reply-To:     cassell.david@EPAMAIL.EPA.GOV
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "David L. Cassell" <cassell.david@EPAMAIL.EPA.GOV>
Subject:      Re: Exact confidence interval for the difference
In-Reply-To:  <OF31E53A6C.88A0C354-ON85257029.0047F25B-85257029.004815B5@hgsi.com>
Content-type: text/plain; charset=US-ASCII

Bob_Abelson@HGSI.COM wrote:
> One of our statisticians wants to know:
>
> Does anyone know if SAS or R can compute an exact confidence interval
for
> the difference
> in 2 binomial proportions?...the only package that I have ever seen do
> this calculation is StatXact...

SAS doesn't do an exact CI for the difference in 2 binomial
proportions.

This is fine by me.  If you read Alan Agresti's 1992 paper "A Survey
of Exact Inference for Contingency Tables", you'll see that he finds
there are problems with defining an 'exact' test in this case.

HTH,
David
--
David Cassell, CSC
Cassell.David@epa.gov
Senior computing specialist
mathematical statistician