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An Alternate Definition of the ETS Delta Scale of Stem Difficulty

Author(s):
Holland, Paul W.; Thayer, Dorothy T.
Publication Year:
1985
Report Number:
RR-85-43, PSRTR-85-64
Source:
ETS Research Report
Document Type:
Report
Page Count:
15
Subject/Key Words:
Delta Index, Difficulty Level, Item Analysis, Statistical Analysis, Test Construction

Abstract

This note develops an alternative definition of the "delta scale" of item difficulty that is used at ETS. A comparison is given with the traditional definition of the delta scale that is based on the normal distribution. Some advantages of the alternative scale are mentioned. (15pp.)

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