Analysis using Generalized Reliability Index of Retest

Abstract

We generalize the index to define the reliability of retest for the cases which have the time shift from the first test to the second test, where the test means questionnaire for a group. The old definition of the index assumes the stability, which means the answers to the test do not change from time to time. However, this assumption is not realistic. The answers of some of the group go up, and some go down. We define the rising point Pu and the descent point Pd, and verified the sum of Pu and Pd give the best expectation value of the time shift by using the least square method. We show the usefulness of the generalized reliability index for several typical examples.