I'm not certain whether I understand your question,
but I use Rasch analysis, and more specifically in
this case, the Rasch rating scale model, when I have
5-point Likert scale items. Rasch analysis allows me
to determine whether any items are misfitting and also
allows me to derive a true interval scaling to obtain
a total score for each person. Although some would
describe the Rasch model as the 1-parameter IRT model
there are conceptual differences underlying both
models.
I do my Rasch analysis with the Winsteps software.
SR Millis
>
> I have a two level structure, items within persons.
> There are five items,
> each measured on a five-point Likert Scale
> (responses are 1,2,3,4,5). I
> need to create a scale for each person based on the
> five items using IRT
> instead of the simple average of items in order to
> make use of all of the
> data. How would I go about this? I can first reshape
> the data, but where
> do I go from there?
>
> For example, my data may look like this originally:
>
> person item1 item2 item3 item4 item5
> 1 3 2 3 4 5
> 2 5 4 2 4 3
> 3 3 2 1 2 2
>
> I can reshape the data into:
>
> person item scale
> 1 1 3
> 1 2 2
> 1 3 3
> 1 4 4
> 1 5 5
> 2 1 5
> 2 2 4
> 2 3 2
> 2 4 4
> 2 5 3
> etc.
>
> What commands might I use to create one scale for
> each person using IRT
> based on the responses to the 5 items?
>
> *
> * For searches and help try:
> *
> http://www.stata.com/support/faqs/res/findit.html
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
Scott R Millis, PhD, MEd, ABPP (CN & RP)
Professor & Director of Research
Department of Physical Medicine & Rehabilitation
Wayne State University School of Medicine
261 Mack Blvd
Detroit, MI 48201
Email: [email protected]
Tel: 313-993-8085
Fax: 313-745-9854
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*
* For searches and help try:
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