skip to main content skip to footer

Notes on Comparable Scales for Test Scores

Lord, Frederic M.
Publication Year:
Report Number:
ETS Research Bulletin
Document Type:
Page Count:
Subject/Key Words:
Equated Scores, Scaling, Scores


If scores on different tests are to be compared, they must have some type of comparability. This paper is concerned with a special type of comparability. It is defined as: when the tests are equally reliable, the score scales will be comparable with respect to a certain group of testees if score distributions of the two tests are identical for this group. The problem is to transform the measurement scale of one of the tests in such a way that the frequency distribution of the transformed scores of this test will be identical with that of the untransformed scores on the other test. Equating means and standard deviations is discussed in five cases. The standard error of converted scores is given for cases 1-5. Equating means and standard deviations are again given for case 6. (SGK).

Read More