Dear all
I am trying to perform a logistic regression without defining a reference
group for the independent discrete variables:
I am intending to determine the ratio of the odds of each of the J levels of
a discrete variable to the average odds (geometric mean of all levels). For
that matter, instead of using the classical reference coding, I followed the
"marginal method". I created dummy variables using the marginal coding:
It means that, instead of coding the jth dummy variable 1 if the discrete
variable is at the jth level and 0 if the discrete variable is at any other
level, I coded the jth dummy variable -1 for the first level, 1 for the jth
level and 0 for the others.
This works beautifully and avoids having a group as reference but brings
another (big) problem: the 1st level doesn�t appear at all in results (not
even as reference...).
How can I estimate a coefficient for level 1?
Thank you for your help
Val�rie Jooste
Val�rie Jooste
Registre des tumeurs digestives
INSERM EMI 0106
Recherche �pid�miologique et clinique en canc�rologie digestive
Facult� de M�decine
BP 87900
21079 Dijon cedex
Tel : 03 80 39 33 25
Fax : 03 80 66 82 51
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