Norm referencing refers to which of the following?

a. The process of measuring overall performance of a group of individuals on two tests that are compared

b. The process of measuring the performance of a group of individuals on a given subset of items on a test

c. The process of measuring performance of each test item on a group of individuals so the average performance of that group can be determined

d. The process of measuring performance of different individuals on each test item on a test to look at different levels of performance