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st: Linear Trend Tests of ORs

From   Young Hee Rho <>
Subject   st: Linear Trend Tests of ORs
Date   Mon, 22 May 2006 19:10:59 +0900 (KST)

I have encountered many "trend tests" of linearity concerning odds ratios (OR) of a
categorical variable.
For example, I am modeling a logistic model Y=b1x1 + b2x2 + b3x3 +b4. x2 is a 5-level
categorical variable, for example the level of drinking (while Y is the presence/absence of
hyperuricemia). When the results are displayed, the ORs of the 5 levels are shown and
the linear trend is shown as a single p value. The individual ORs may not have significance,
however the overall trend does. It is said that it was tested through regressing the median of
the levels on the ORs. Otherwise in other cases, there are many trend tests of linearity
expresed in many papers, however, the actual method is not explained in detail. (It does not
apear to come from polynomial contrasts of ANOVA nor from categorical trend tests
(Cochrane-Armitage) since the arformentioned test is from values coming from
one categorical variable having several estimates. How is this done and how much methods
exsist on this topic? Are there any useful references?
** For those who got twice this article, I sent this article again since it did not seem to register on
Statalist. Many apologies if there was a duplicate delivery.

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