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Equating Test Scores -- The Maximum Likelihood Solution for a Common Equating Problem

Lord, Frederic M.
Publication Year:
Report Number:
ETS Research Bulletin
Document Type:
Page Count:
Subject/Key Words:
Equated Scores, Maximum Likelihood Statistics, Tucker, Ledyard R


The maximum likelihood solution is presented for the following equating problem: Two tests, U and V, are to be equated, making use of a third "anchor" test, W. The examinees are divided into two random halves, which will be called the "a-group" and the "b-group." Tests U and W are administered to the a-group; tests V and W are administered to the b-group. It is assumed that any practice effect or other effect, exerted by U and V on W, is the same for U and for V. The solution obtained differs from that introduced at ETS by Tucker only in the initial assumptions from which it is derived.

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