[Rasch] Question about difficulty and ability parameters in item response theory

Mike Linacre mike at winsteps.com
Wed Aug 14 19:06:31 EST 2013

Fatemeh Khalesi:

A formula for estimating item discrimination is shown in 

Ranking students is usually based on their person ability estimate 
(theta). See Mark Moulton's spreadsheet for the Rasch Model.

2-PL IRT estimation is more complicated. There are free R Statistics 
procedures available, see 

Mike L.

On 8/14/2013 0:52 AM, fatemeh khalesi wrote:
> My problem is assessment test-takers based on item response theory 
> model and i don't know how it's estimate discrimination parameter (a) 
> and ranking students.

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