[Rasch] Re-calibration Procedure

ranganaths ranganath.s at excelindia.com
Mon Jun 21 15:13:19 EST 2010



            It is well known that in the case of CAT, for the item to be
included in the item bank, It needs to be calibrated and this happens over a
period of time on administering the item in various tests. Say for eg, we
have administered test1, test2.  testn the same question Q1. The item Q1
gets item parameter value a1,b1 and c1 in test1. The response vector being
v1 for the item Q1 in test1. In the successive tests should the response
vectors(v1,v2 . vn) for the same item Q1 be merged with the previous test
response to get the calibrated value of a1, b1 and c1.




Is it enough to have the a1, b1 and c1 value and then proceed having similar
values for the item in different tests and then take average of the
corresponding values to arrive at the final a, b and c values.




Ranganath S

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