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Re: st: Interpretation of interaction term in nonlinear models


From   Suryadipta Roy <sroy2138@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Interpretation of interaction term in nonlinear models
Date   Thu, 30 May 2013 12:10:58 -0400

Maarten,
Thank you very much for the suggestion! I am going to follow it up carefully.

Sincerely,
Suryadipta.

On Thu, May 30, 2013 at 11:26 AM, Maarten Buis <maartenlbuis@gmail.com> wrote:
> It often helps to include the reference category for one of the
> categorical variables:
>
> M.L. Buis (2012) "Stata tip 106: With or without reference", The Stata
> Journal, 12(1), pp. 162-164.
>
>
> Hope this helps,
> Maarten
>
> On Thu, May 30, 2013 at 4:52 PM, Suryadipta Roy <sroy2138@gmail.com> wrote:
>> Dear Maarten and fellow Statalisters,
>>
>> I actually had a related question as to whether there might be a
>> similar (one-sentence) interpretation in case of a three-way
>> interaction between the same categorical variable, the continuous
>> variable with another categorical variable (0/1). Of course, I can and
>> have used -margins - with -marginsplot- to show how the interaction
>> effects differ in the presence of this categorical variable, but I was
>> wondering if I could get some help with an easier interpretation. The
>> coefficient of the three-way interaction term (standardized continuous
>> by categorical by categorical) in the fixed effects Poisson regression
>> with the -irr- option is 0.74 and in the probability metric form is
>> -0.21. Once again, thank you very much for the help!
>>
>> Sincerely,
>> Suryadipta.
>>
>> On Thu, May 30, 2013 at 7:53 AM, Suryadipta Roy <sroy2138@gmail.com> wrote:
>>> Maarten,
>>> This is very helpful, thank you very much! For some reason, I thought
>>> that the z_phd variable in your example is a categorical variable as
>>> well when I had previously read the thread. I guess that I would need
>>> to standardize my continuous variable for a similar interpretation.
>>>
>>> Sincerely,
>>> Suryadipta.
>>>
>>> On Thu, May 30, 2013 at 7:19 AM, Suryadipta Roy <sroy2138@gmail.com> wrote:
>>>> Dear Statalisters,
>>>>
>>>> I am studying the effect of an interaction between a categorical
>>>> variable (0/1) and a continuous variable (0-6) on the dependent
>>>> variable in a nonlinear model (using -xtpoisson-). The value of the
>>>> coefficient using the -irr- option is 0.90, while the size of the
>>>> interaction term in the probability metric form is, of course, -0.11
>>>> (exp(-0.11) = 0.90). My basic question is, if it might be possible to
>>>> have a one-sentence interpretation of the value of the coefficient in
>>>> the multiplicative form (0.90), e.g. something in the lines of "the
>>>> effect of the categorical variable increases by a factor of 0.9 (i.e.
>>>> a 10% reduction of the dependent variable) due to an 1% increase in
>>>> the continuous variable"? Any suggestion in this regard will be highly
>>>> appreciated.
>>>>
>>>> Sincerely,
>>>> Suryadipta Roy.
>>>> *
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>
>
>
> --
> ---------------------------------
> Maarten L. Buis
> WZB
> Reichpietschufer 50
> 10785 Berlin
> Germany
>
> http://www.maartenbuis.nl
> ---------------------------------
> *
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