[Rasch] CAT Questions

ranganaths ranganath.s at excelindia.com
Fri Jan 29 00:35:21 EST 2010



     Thanks for the response. I still have a doubt about the practical
implementation of the IRT. 

1. Lets assume that I have started IRT from scratch. I have a list of
questions to be administered to a group. For each of the question I know
only whether the question is easy, medium or hard, the values of   

    the item parameters are unknown for me. Is it required to calibrate the
items in the test and find out the item parameters before it is
administered? If yes

2. Is it required to administer each and every new item to a sample group
ascertaining the item parameters before it is given to the real examinees?

3. What advantage does the IRT implementation gives to the tutor who is
supposed to take the remedial teaching, which anyway can also be taken from
any kind of conventional testing methodology?

4. I have read in an article that the CAT helps in reducing the test timings
and also it could be administered at time independent fashion still
measuring the examinees ability on the same scale, Are these the only
advantages of using IRT? IF any other advantage is there over the
conventional methodology please explain.



Ranganath S



From: Mike Linacre (RMT) [mailto:rmt at rasch.org] 
Sent: Thursday, January 28, 2010 10:41 AM
To: rasch at acer.edu.au
Subject: Re: [Rasch] CAT Questions


Thank you for asking us, Ranganaths.

You asked:

1. I am wondering how the IRT in its computer application version called CAT
useful in accessing a student?.

Answer: CAT is useful and effective. Each student can have a customized test
with increased security and flexible test scheduling. relative to
paper-and-pencil tests.

You asked:

2. What question types are used for CAT?

Reply: Any type that can be computer-scored. Multiple-choice questions are
the most common.

You asked:

3. Which of the 3 models 1P, 2P and 3P is useful for a correct judgment of
the students ability?

Reply: In practice, 1P (Rasch) is the most practical model for item
selection and ability estimation for items scored right/wrong.

You asked:

4. Which book is best suited to know the advanced form of IRT for the real
application of it?

Reply: You could start with a Google search of www.rasch.org
<http://www.rasch.org/>  for documents explaining basic CAT concepts. Then
Google-search the Internet for documents and books relating to more complex
topics, such as CAT test security and CAT item exposure.

Mike L.

Mike Linacre
Editor, Rasch Measurement Transactions
rmt at rasch.org www.rasch.org/rmt/ Latest RMT:  23:2 Autumn 2009

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