Differential Item Functioning

Differential Item Functioning

Differential Item Functioning

Differential Item Functioning


Test fairness is a moral imperative for both the makers and the users of tests. This book focuses on methods for detecting test items that function differently for different groups of examinees and on using this information to improve tests. Of interest to all testing and measurement specialists, it examines modern techniques used routinely to insure test fairness. Three of these relevant to the book's contents are:

• detailed reviews of test items by subject matter experts and members of the major subgroups in society (gender, ethnic, and linguistic) that will be represented in the examinee population

• comparisons of the predictive validity of the test done separately for each one of the major subgroups of examinees

• extensive statistical analyses of the relative performance of major subgroups of examinees on individual test items.


The Manpower and Personnel Division of the Air Force Human Resources Laboratory, part of the Air Force systems Command, was pleased to have cosponsored a conference on DIF with the Educational Testing Service. We have long been partners in psychometric progress. The purpose of the American military is to deter aggression and defend against those who would deprive us of our rights. This is done in a manner consistent with fair treatment and equality. The twin ideas of human rights and fair treatment of humans have been advanced rapidly by the American military in this century. From the World War I committee of the American Psychological Association that met in Vineland, New Jersey to the 1948 presidential order integrating the armed services three decades later, to support for advanced psychometric models of fairness, to this conference, America's military research establishment has been in the forefront of development and fair application of advanced technology.

DIF is of concern to the Air Force and to all major test developers and users. The American military is in a unique position because we develop and use our own tests. This year, more than two million young men and women will be tested for enlistment qualification and additional hundreds of thousands of tests will be administered by the service for promotion and certification purposes. These tests will materially affect the lives of these military members and the security of our country.

The issue of test and selection fairness encompasses many concepts and models. Primary to all of them is DIF. If test items operate in a differential fashion, then the scores for different groups are per se not comparable. This cannot lead to equitable treatment, a declared goal of the American armed forces. For the Air Force, which produces both enlisted and officer tests, certain models . . .

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