Posted by
Rich Ulrich on
Sep 23, 2019; 7:18pm
URL: http://spssx-discussion.165.s1.nabble.com/Re-Main-and-interaction-effect-in-Cox-Prop-Hazards-tp5738390p5738403.html
By the way - I would like to add - do not present the Age effect, when you get that far,
as the B coefficient = 1.089. That is the increase in the OR for risk for a /single/ year. As a
"risk", it is not nearly commensurate with the values of the risks you produce for your
dichotomous items.
There are a couple of approaches for handling this. One that does not depend on the
range of ages in the sample is run the run with an alternate version of age, like, AGE10 = AGE/10 .
The test-statistics remain exactly the same, but the new "effect" is the risk per decade of age,
and will be 2.346 (if I've picked the right formula - raise 1.089 to the power of the number
of years, which is 10).
The approach which gives values that are even more commensurate to the dichotomies is
to compare the risk at the range of plus-and-minus one standard deviation of the age range.
How many years? - raise 1.089 to that power. That one would do more to emphasize that
Age is by far the strongest effect according to the Wald tests.
--
Rich Ulrich
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