Date: Wed, 9 Apr 2003 09:56:10 -0700
Reply-To: Dale McLerran <stringplayer_2@YAHOO.COM>
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: Dale McLerran <stringplayer_2@YAHOO.COM>
Subject: Re: test for proportions
In-Reply-To: <8kd89vsbncq9ihkb8cnblqtcov1qqeknu3@4ax.com>
Content-Type: text/plain; charset=us-ascii
In addition to testing each row separately, you can sum the
chi-square values for each row and test this against the
chi-square distribution with df=5*9. I would look at this pooled
test first, and if it is significant then examine the row-specific
chi-square tests. If the pooled test is not significant, do
not interpret the row-specific tests. You are introducing a
multiple comparisons problem with the multiple row-specific tests.
If you examine row-specific tests conditional on the the pooled
test, you effectively control the experimentwise error rate.
Dale
--- Jay Weedon <jweedon@EARTHLINK.NET> wrote:
> On 9 Apr 03 00:13:56 GMT, ctsdias@CARPA.CIAGRI.USP.BR (Carlos Tadeu)
> wrote:
>
> >I am working in an assessorship in a problem of contingency table
> 5x10 and the researcher wants to know if there are difference among
> proportions inside a level of the first factor. I would like to know
> if there is a test for this in the SAS and where I can find
> references about. This sound like multiple comparison of proportions
> in a contingency table that has one row and 10 columns.
> >
> > A B C D E F G H I J K total
> >M p1 p2 p3 p4 p5 p6 p7 p8 p9 p10 N
> >
> >Where pi=Ni/N, AND sum(Ni)=N
>
> Generate one-way frequency tables and request the chi-square test,
> e.g.,
>
> proc freq;
> tables column /chisq;
> by row;
> run;
>
> This will generate (separately for each row) a chi-square
> goodness-of-fit test of the null hypothesis that the row proportions
> are all equal.
>
> JW
=====
---------------------------------------
Dale McLerran
Fred Hutchinson Cancer Research Center
mailto: dmclerra@fhcrc.org
Ph: (206) 667-2926
Fax: (206) 667-5977
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