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st: Number of degrees of freedom
From
Nikolaos Pandis <[email protected]>
To
[email protected]
Subject
st: Number of degrees of freedom
Date
Sat, 27 Feb 2010 02:09:59 -0800 (PST)
Hi to all.
I would like to ask:
Let us say we run a Cox model with 2 predictors A and B, where A has 4 levels and B has 2 levels.
Then you run the same model plus the A*B interaction term and perform an
-lrtest- to check if the interaction is significant.
How many degrees of freedom would this test have? Is it 3?
Why?
Is it because 3 extra parameter are included in the second model as we look at the output?
Do we count the difference in the number of parameters in the output between the 2 models or the difference in the number of parameters in the command line? The latter will indicate only 1 parameter difference i.e the intarction term
Many thanks,
Nick
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