An Item-Discrimination Index Is Used on an Ability Test

Multiple Choice

An item-discrimination index is used on an ability test

A) to determine whether items are measuring what they are designed to measure.
B) to measure the difference between how many high scorers and how many low scorers answered the item correctly.
C) to estimate how predictive the item is of the testtaker's future performance.
D) to measure the difference between how many median scorer and how many low scorers answered the item correctly.