[Rasch] Rating scale and partial credit model with identical responses

Mike Linacre rmt at rasch.org
Mon Jun 26 23:13:36 EST 2006

Dear Rama:

Thank you for your question - it addresses an important issue in 
statistical analysis.

These "perfect" response strings are a problem for any type of analysis! 
These response strings are like putting each student's MCQ bubble sheet 
through an optical scanner 5 times, and then thinking that you had 5 
observations of each student's responses to each item.

If you really have a dataset like this, then 4 of the 5 judges are 
redundant, and their data should be eliminated. It provides no extra 
statistical information.

You would then have only one statistically-independent observation of each 
student. This is enough to order the students, but not enough to construct 
a verifiably linear measurement system.


Mike L.

At 6/26/2006, you wrote:

>Dear all,
>If  on a set of polytomous items or Likert scale items students get the
>same score on each individual item, is it a problem for Rasch analysis?
>Suppose, the response vectors for 5 polytomous items for 5 respondents
>And this pattern continues for all respondents.
>This could well be the case when there is complete agreement among
>judges in rated performances, which could be the result of good training
>and the existence of a well defined rating scale.
>Tried the new MSN Messenger? It's cool! Download now. 
>Rasch mailing list
>Rasch at acer.edu.au

Mike Linacre, mike at winsteps.com
Winsteps, PO Box 811322, Chicago IL 60681-1322
Tel. & FAX (312) 264-2352
Facets Introductory Workshop: www.winsteps.com/facwork.htm - July 28-29, 2006
Winsteps Introductory Workshop: www.winsteps.com/workshop.htm - Aug. 7-8, 2006
Winsteps Online Course: www.statistics.com/courses/rasch - July 21 - Aug. 
18, 2006
Winsteps: www.winsteps.com/winsteps.htm - current version 3.61.1 - May 2006
Facets: www.winsteps.com/facets.htm - current version 3.61.0 - May 2006
Your comments and questions are welcomed.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://mailinglist.acer.edu.au/pipermail/rasch/attachments/20060626/ade4c8f7/attachment.html 

More information about the Rasch mailing list