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# RE: st: 1-4 scale

 From Ebru Ozturk To Subject RE: st: 1-4 scale Date Sat, 4 Aug 2012 21:10:20 +0300

```Dear David,

Thank you. By a factor variable, do you mean factor analysis? as I didnt understand why the model will have three coefficients.

----------------------------------------
> Date: Sat, 4 Aug 2012 08:26:43 -0400
> Subject: Re: st: 1-4 scale
> From: dchoaglin@gmail.com
> To: statalist@hsphsun2.harvard.edu
>
> Dear Ebru,
>
> Your options probably depend on how much data you have.
>
> In some areas, it is customary to assign the values 1 through 4 to
> each question, form the sum of the four questions in each of the two
> headings, and use those two variables in your model. Centering is
> probably not important at this stage.
>
> That approach chooses one particular way of combining the four
> questions in each heading. To let the data choose the combination,
> you can use all eight questions in your model, instead of the two
> sums. You should probably check that no two questions are highly
> correlated.
>
> If you have enough data, you can (as Nick suggested) use a factor
> variable for each question. Then your model will have three
> coefficients for each question. This approach avoids the assumption
> that the response categories for a question are equally spaced.
>
> I would not exclude the possibility of interactions between questions.
> In principle, you can cross-classify the data on the eight questions,
> but the full cross-classification would have 4^8 = 2^16 cells. For
> the separate sets of four questions, the cross-classification would
> have 256 cells.
>
> David Hoaglin
>
> On Sat, Aug 4, 2012 at 6:24 AM, Ebru Ozturk <ebru_0512@hotmail.com> wrote:
> >
> > Dear All,
> >
> > I have a question on how to add a variable that includes items measured by likert scale to the estimation model.
> >
> > For instance, in the data there is one question that measures the objectives of innovation activities. The answers to the question include 8 items that have been measured by 1-4 scale. I will split them into two headings as they focus on two types of objectives. Thus, for each 4 item how do I add them to the model? Because it is 1-4 scale so do I need to mean centred them or do something else?
>
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