topic Comparions/P-value/right test in sas in Statistical Procedures

Comparions/P-value/right test in sas

ChristinaWang — Thu, 26 Apr 2012 16:17:15 GMT

Hi,

I have a dataset that looks like the following,

variable x :1 = very worried, 2 = slightly worried ,3 = Not worried

variable y : 1 = more likely, 2 = no change ,3 = less likely
I would like to comparsion the factor variable x and outcome variable y.

Which 's test inside sas will give the right p-value?

Thanks.

Re: Comparions/P-value/right test in sas

PGStats — Thu, 26 Apr 2012 16:43:50 GMT

A good general purpose test for the relationship between two categorical variables is Fisher's exact test. If your number of observations is not too large ( < 100 say), use the following :

proc freq data=myData;

tables x*y;

exact Fisher / maxtime=20;

run;

If the computation doesn't terminate within 20 seconds, add the MC option to the EXACT statement.

Re: Comparions/P-value/right test in sas

Doc_Duke — Thu, 03 May 2012 14:33:40 GMT

Christina,

"Right" is a very slippery term in this sort of analysis. There is probably no single answer. There is a huge literature on testing association among ordered variables.

The Fisher's Exact Test that PG recommended is a general purpose test that could be used, but it is known to be conservative. If your sample size is larger, then you could use the Chi-Squared test that is part of PROC FREQ to address general association.

Neither of these tests take advantage of the inherent ordering of the two variables. I prefer Kendall's Tau-b (also part of FREQ).

Doc Muhlbaier

Duke