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Effects on Score Distribution of Deleting an Unkeyable Item From a Test SAT

Dorans, Neil J.
Publication Year:
Report Number:
ETS Research Report
Document Type:
Page Count:
Subject/Key Words:
Equated Scores, Item Analysis, Psychometrics, Scaling, Scholastic Aptitude Test (SAT), Statistical Analysis, Test Construction


A formal analysis is presented of the effects of item deletion on equating/scaling functions and reported score distributions. The phrase "item deletion" refers to the process of changing the original key of a flawed item to either all options correct, including omits, or to no options correct, i.e. not scoring the flawed item. There are two aspects to the present analysis. The first aspect is analytical, focusing on the development of a formal model for the item deletion effect by decomposing it into its constituent elements. The second component of the analysis is empirical, involving the use of actual Scholastic Aptitude Test data to illustrate and supplement the analytical results. The analytical decomposition demonstrates how the effects of item properties, test properties, individual examinee responses and rounding rules combine to produce the item deletion effect on the equating/scaling function and candidate scores. In addition, the analytical component of the report examines the effects of not scoring vs. scoring all options correct and the effects of re-equating vs. not re-equating, as well as the interaction between the decision to re-equate or to not re-equate and the scoring option chosen for the flawed item. (Author/PN). (60pp.)

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