Message-ID: <HDX7Y7$909739BCA8E8339FC66D1B83417BECD8@libero.it>
Date: 2003-04-25T22:32:31Z
From: Simona Avanzo
Subject: problem in a glm model.
Hallo all,
I have a problem in a glm model.
The glm model has, among the other variables, 4 dummy variables:
flg.a2 (takes values 0 or 1)
flg.d.na2 (takes values 0 or 1)
flg.v2 (takes values 0 or 1)
flg.cc2 (takes values 0 or 1)
In addition to these variables, I have included their interaction, with the order:
(flg.a2+flg.d.na2+flg.v2+flg.cc2)^2
In the model?s summary there are not some interactions (flg.a2:flg.cc2 e flg.d.na2:flg.cc2), because there are not cases that present these interactions.
Then, the model?s summary shows that the p-value of the interaction flg.a2:flg.d.na2 is 0.66, and so this interaction can be eliminated.
But when I apply the test anova between the model whit this interaction and the model without this interaction, the p-value is 0.004, and so, the interaction is significative.
Why I obtain this difference?
Many thanks for any help,
Simona