Re: st: Count data interaction terms

[DA Gibson <DAGibson1@sheffield.ac.uk>]

HI Maarten

Thanks a lot for that.

Cheers

Danny

On 23 August 2011 11:12, Maarten Buis <maartenlbuis@gmail.com> wrote:
> On Tue, Aug 23, 2011 at 11:40 AM, DA Gibson <DAGibson1@sheffield.ac.uk> wrote:
>> Hi Maarten
>>
>> Thanks for that, i do have one further question however. In the
>> example the IRR on the c.persons#c.child interaction term is positive
>> at .77 however in your email you say that the interpretation is that
>> the effect is reduced.
>
> These effects are ratios rather than differences, so any number less
> than 1 is a "negative" effect. If you multiply some number with a
> number less than one, than the result will be smaller than the
> original number. You can transform ratios into percentage changes by
> doing (ratio - 1)*100%, i.e. multiplying the effect of persons by
> 0.77, is equivalent to saying that the effect of persons changes with
> -23% when the extra person is a child.
>
> Hope this helps,
> Maarten
>
> --------------------------
> Maarten L. Buis
> Institut fuer Soziologie
> Universitaet Tuebingen
> Wilhelmstrasse 36
> 72074 Tuebingen
> Germany
>
>
> http://www.maartenbuis.nl
> --------------------------
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