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Re: st: Creating Scale with Ordinal Data using IRT


From   n j cox <[email protected]>
To   [email protected]
Subject   Re: st: Creating Scale with Ordinal Data using IRT
Date   Thu, 11 Jan 2007 16:27:17 +0000

The abbreviation "IRT" which is here assumed familiar to
all I understand to mean "item response theory".

A -findit item response theory- finds some items. -findit IRT-
finds some more (and some false positives).

I have no idea whether any is the answer to your question.

Nick
[email protected]

[email protected]

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?

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