[Rasch] RSM & PCM

Anthony James luckyantonio2003 at yahoo.com
Wed Mar 3 19:17:06 EST 2010



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Dear All, 

I know that
this is a very old and probably a boring question for many of you. But I need
to know this 

What is the
difference between rating  scale model
and partial credit model? 

What I have
gathered is that in RSM the distances between the points on the scale is equal
and this distance is the same for all the items in the instrument. That is, the
ability difference needed to endorse 3 rather than 2 is the same as the ability
difference needed to endorse 5 rather than 4. Right? 

In PCM,
however, the distances between points on the scale is unequal  both within the items and between the items in
the instrument. That is, the ability increment to score 3 on an item rather
than 2 is not the same as the ability increment needed to score 6 rather than
5. And these distances are unequal among  the items in the test. Right?
 

Cheers 

Anthony 

   




      


      

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