03-15-2014 07:50 PM
I have a question regarding proc rank. I created quartiles in sas using proc rank and then ran phreg afterwards for my model. my output however has 2 parameter estimates instead of 3 (I set the lowest quartile as the reference) Can anyone explain to me why that I have only 2 parameter estimates? Thanks!
03-15-2014 11:38 PM
When I run proc freq, for level=0 (reference) I have a total of 16,875 people, level=2 11,014 and level=3 9,086 for a grand total of 36,975...so level=1 doesn't show up. I guess there was no one that had a value that fell into that particular quartile?
03-15-2014 11:44 PM
You must have a large fraction of hisugbev values that are tied... You should reconsider the way you divide up that variable if you want to get a meaningful model.
03-15-2014 11:49 PM
Take a look at your actual values in a histogram to decide a distribution. Sometimes there's genuine data intervals visible.
Make sure to add the param=ref option as well, sorry to repeat that.
03-16-2014 08:31 PM
I ran proc univariate for the variable hisugbev and it is very left-skewed, about 65% of the observations have a value of 0 so that would probably explain the missing parameter estimate. My professor said I can still create quartiles even with the skewed data. Is there any sort of ideas you may have in mind? The data goes from 0-18 so i thought i could do maybe like 0-4, 4-8, 8-12, 12+
03-16-2014 09:36 PM
It would probably make sense. To be sure, try looking at the distribution of uncensored events:
ods graphics on;
Proc univariate data=temp4;
where c5_1 ne 0;