Ricardo, it is my understanding that by including the ordered variable
as continuous, the test performed on the coefficient is equivalent to
a trend test, adjusting for the covariates in the model. Steve
Selvin's book, "Statistical Analysis for Epidemiologic Data" (second
edition) has a discussion of this on page 228.
On 1/25/06, Ricardo Ovaldia <[email protected]> wrote:
> Dear all,
>
> I am using logistic regression to model the effect of
> an ordered categorical variable (at 4 levels) on
> mortality while adjusting for other covariates.
> Indicator variables for the categorical variable were
> used in the model. The estimated odd ratios from the
> logistic model for these indicator variables increase
> with the order of the variable. Although, there is a
> trend I would like to formaly test it.
>
> I tryed using -tabodds- and -mhodds- but it does not
> work well when adjusting for continous variables.
>
> I then simply included the ordered categorical
> variable as continous and re-ran the model. Is the
> test performed on this new coefficient a valid test
> for trend, although the model is nolonger the same?
>
> Is there a better way to do this in Stata?
>
> Thank you,
> Ricardo.
>
>
>
> Ricardo Ovaldia, MS
> Statistician
> Oklahoma City, OK
>
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