The impact of the errors of equating and errors of measurement on the reported scores
Methodology exists for computing the indices of two sources (errors of measurement and equating) of instability, separately. In this research, a way of combining both sources of instability conditional on the true ability (theta) of a test-taker is developed and applied to the 2005 AP English Language and Composition test. The findings indicate that the majority of the impact is due to errors of measurement and the errors of equating contribution are minimal.
Mekhael, Michael, "The impact of the errors of equating and errors of measurement on the reported scores" (2008). ETD Collection for Fordham University. AAI3308284.