[Rasch] item bank

Svend Kreiner S.Kreiner at biostat.ku.dk
Thu Oct 12 18:20:20 EST 2006


I am not sure I understand this. I thought that the whole idea about 
specific objectivity in Rasch models was the (relative) difficulties of 
items does not depend on the sample of persons and on whether or not 
other items are included in the test.

The item parameters only provide measures of relative difficulties, e.g. 
the difference between the difficulty of item A and item B. This 
difference is the same whether or not you have observed a response to 
item C. So in which sense is the difficulty of items A and B reduced by 
inclusion of C in the item bank?

Best regards

Svend Kreiner

Agustin Tristan skrev:
> Another thing Iasonas:
> Once you have an "open" item bank, is it useful to calibrate the 
> items? the difficulty of the items will ve reduced, even most of them 
> will be solved by mostly all people...so the initial calibration has 
> nothing to do with the original calibration.
> This is another important topic to discuss.
> Regards
> Agustin Tristan
>
>
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-- 
Svend Kreiner
Associate professor
Department of Biostatistics  
University of Copenhagen 

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