st: clogit data format

[Margaret R Grove <margaret.r.grove@Dartmouth.EDU>]

Hi,

I'm attempting to use clogit and have a very basic question about the 
data format.  It seems like it should be obvious but I'm getting very 
different answers than a colleague using SAS PHREG.

The data looks like this:

id    rater    rating
1      1          0
1      2          1
1      3          1
1      4          0
2      1          1
2      2          .
2      3          0
2      4          0
etc.

I want to look at the difference between raters (have already done 
kappa).  I tried:

xi: clogit rating i.rater, group(id)

but, I get different results than with PHREG.

What am I doing wrong?  Am I misunderstanding clogit?

Thank you!

Margaret

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