Why my contrast statement gave me only one p-value?

[twotwotwo]

Hi,

I performed a mixed model procedure and in this procedure, I used group as the fixed effect.  The group is a categorical variable and has 4 level.  And I want to compare the difference between each group with the contrast statement.  Here is my code:

proc mixed data=test;

by brand;

class name;

model price=group;

contrast 'group1 vs2' group 1 -1 0 0;

contrast 'group1 vs3' group 1 0 -1 0;

contrast 'group1 vs4' group 1 0 0 -1;

run;

However, I got 3 SAME contrast p-value.  But those 4 groups are different from each other.  Why I got the same p-value for those 3 comparisons?  Thanks!

[art297]

Seeing the data might help someone trying to answer your question.

[twotwotwo]

Thanks for your response. Please see the attached.  I only put part of my data.  Thanks.

[twotwotwo]

Please see my attachment for the data.  Thanks!

[Doc_Duke]

I think that the problem is in your CLASS statement.  I think that it should read

CLASS group;

Doc Muhlbaier

Duke

[twotwotwo]

Thanks for your reply.  I really want CLASS name; How can I correct them? thanks!

[Reeza]

SAS isn't considering GROUP a categorical variable if its not in the class statement.

You might want to include in your BY statement perhaps, ie a separate model for each value of name? or you can have both in the class statement.

CLASS group name;

Not sure, depends on what you're trying to do.

[twotwotwo]

Thanks!  It then gave me three different p-value.