Equating Test Scores: Toward Best Practices

Score equating is essential for any testing program that continually produces new editions of a test and for which the expectation is that scores from these editions have the same meaning over time. Different editions may be built to a common blueprint and designed to measure the same constructs, but they almost invariably differ somewhat in their psychometric properties. If one edition is more difficult than another, examinees would be expected to receive lower scores on the harder form. Score equating seeks to eliminate the effects on scores of these unintended differences in test form difficulty. Score equating is necessary to be fair to examinees and to provide score users with scores that mean the same thing across different editions or forms of the test.