American Statistical Association
New York City
Metropolitan Area Chapter

Mailman School of Public Health
Columbia University
Department of Biostatistics Colloquium



DIFFERENTIAL ITEM FUNCTIONING IN A GRADED RESPONSE IRT MODEL:
A BAYESIAN APPROACH TO ITEM DISCRIMINATIONA

by

Mark Glickman
Boston University


Abstract

Mental health survey instruments are often useful at diagnosing and summarizing well-being of respondents. A typical survey involves respondents evaluating themselves on a number of items via a set of ordinal choices. If certain subgroups of patients with the same mental health status give systematically different responses to certain items, the instrument is said to exhibit differential item functioning (DIF). In this talk, we develop a Bayesian approach to identifying differences in item response patterns with particular application to Samejima's (1969) graded response model. Our approach involves positing four lack-of-fit diagnostics to examine departures from conditional independence. We apply our approach to the analysis of responses by mental health patients from the BASIS-24, a widely-used self-report mental health assessment instrument, to study differences among different cultural and language groups in item response patterns.

This is joint work with Pradipta Seal (Boston University) and Susan Eisen (CHQOER/BUSPH).


Date: Thursday, March 22 2007
Time: 4:00 to 5:00 P.M.
Location: Mailman School of Public Health
Department of Biostatistics
722 West 168th Street
Judith Jansen Conference Room (Room 425)
New York, New York

RESERVATIONS ARE NOT REQUIRED

Refreshments will be served at 3:30 P.M. in the
Biostatistics Conference Room (Room 627).


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