[Rasch] Using Winsteps to compute scores

Bond, Trevor trevor.bond at jcu.edu.au
Tue Feb 5 12:21:07 EST 2013


A straight line - give or take the error estimates.

Sent from 007's iPad

On 05/02/2013, at 11:18 AM, "Tom Conner" <connert at msu.edu<mailto:connert at msu.edu>> wrote:

Do the entire set of items fit when analyzed together?  Do the items in each subscale fit when analyzed separately?  Are the items in the subscales all theoretically measuring the same concept?

tlc

On 2/4/13 5:05 AM, Juanito Talili wrote:
We developed a 36-item self-administered survey instrument that will be used to measure the performance of "recollection facilitators".  The instrument consists of five subscales with items that used a five-point ordered response options. For the scoring, it is tedious in the part of the user if the scores shall be computed by subscale.  Thus, we plan to rasch analyze the entire scale (the 36 items together) and then produce the scores by respondents across items using Winsteps.  Then, from that scores, the user can easily compute the scores by subscale.  However, we afraid because Rasch analysis of the entire scale, instead of by subscale, might be wrong.  To check if we are not wrong, we do the two analyses as follows:
Analysis 1: We Rasch analyze by subscale and then produce the scores by subscale.
Analysis 2: We Rasch analyze the entire scale and then produce the scores by subscale.

Then, for each subscale we will draw scatterplot of the scores generated from the two analysis.  Analysis 1 and analysis 2 are the same if the points in the scatterplot will form a straight line.  Are we correct?

Any comments are welcome.

Thank you.
J



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--
Tom Conner
Professor Emeritus
Department of Sociology
Michigan State University
"What if there were no hypothetical questions?"


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