Hi,

I'm helping my wife with some logistic regression in SAS and we've run into

a little problem regarding interpretation of interaction terms.

We have a model of where Sex, Age as well as the interaction term Sex*Age

seems to be signification effect terms.

Sex is just a two level variable (no surprises there;-), but Age is not

continuous; it has three levels 5th, 7th and 9th grade.

The issue is that SAS only provides two estimates of coefficients for the

Sex*Age interaction term - one for Boys in the 5th grade and one for Boys in

the 9th grade.

How do you interpret this?

We'd like to calculate odds ratios for the age groups seperately for boys

and girls which requires some hand calculations since SAS does not calculate

these when an effect is included in an interaction term, but we do not know

how to do this.

And how would you present these results? Any pointers to examples will be

welcomed dearly!

My wife's teacher has suggested that we split the data set into two: one for

boys and one for girls.

This effectively removes the interaction, but it seems to be a statistically

troublesome approach to me: a lot of things ceases to be statistically

significant and it becomes harder to compare the boys and girls - or am I

wrong here?

Thanks in advance

/Torben

--

P.S. The views expressed above are my own.

P.P.S. Remove dashes in address to reply.