it's fine - you do it in exactly the same way you do any other
interaction - in SPSS (or most other packages) just stick in the
interaction effect.
J
On 28 January 2010 14:28, Ioanna Vrouva <[log in to unmask]> wrote:
> Dear All,
> any ideas would be most appreciated.
> In a logistic regression predicting outcome (self-harm at 24 months yes or
> no), we are interested in whether treatment model (A or B) and
> self-mutilation at intake (present or absent) interact.
> Is it possible to compute an interaction term based on these two independent
> dichotomous variables (as one could do in the case of 2 continuous IDs) , as
> the samples are not very large?
> If this does not make sense, would the way to go about this be to split the
> file into say those who self-harmed at intake and those who did not, and
> look at treatment model as a the only ID?
> many thanks
> Ioanna
>
--
Jeremy Miles
Psychology Research Methods Wiki: www.researchmethodsinpsychology.com
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