Date:         Tue, 22 Dec 1998 11:40:22 GMT
Reply-To:     Javier <jportela@EUCMAX.SIM.UCM.ES>
Sender:       "SAS(r) Discussion" <SAS-L@UGA.CC.UGA.EDU>
From:         Javier <jportela@EUCMAX.SIM.UCM.ES>
Organization: s
Subject:      Re: Still have problem with Chi Square...
Content-Type: text/plain; charset=us-ascii

>The SAS syntax to generate the probability
>of a chi-square statistic should be:
>
>   pvalue= 1 - probchi(chi, df);
>
>where for this application, df=3.
>
>NOT:
>>                pvalue=probchi(N-1,chi);
>
>The latter syntax, swaps the position of
>the chi-sqaure varaite and the model df and
>does not subtract the obtained quantity
>from unity.
>
>
>A chi-square of 6.35 judged against 3 df
>has a p-value of 0.0955--not 0.1605.
>Still, the null should be rejected at
>conventional levels of statistical
>significance.
>
>
>
>Steve Gregorich
>
 
That's true.
 
probchi(df,x)=P(X<=x), were X is the random variate chi-square with df degrees
of freedom.
 
And the p-value is the probability of the "right tail area" under the
distribution, from x to infiny...
 
So change          probchi(N-1,chi)
 
        by
 
                1-probchi(N-1,chi)
 
        in the program.
 
(It gives P=0.838986911, not 0.0955, i do not understand Steve's result. You
should accept H0.)
 
Thanks, Steve, and sorry, Harvey.