A Note on the Item Information Function of the Four-Parameter Logistic Model. (June 2013)

• Record Type: Journal Article
• Authors: Magis, David
• Is Part Of: Applied psychological measurement. Volume 37:Number 4(2013)
• Page Start: 304
• Page End: 315
• Publication Date: 2013-06
• Subjects: item response theory -- four-parameter logistic model -- item information function -- maximization; Psychometrics -- Periodicals; Psychological tests -- Periodicals; Psychology, Applied -- Periodicals; 150.1519505
• DOI: 10.1177/0146621613475471
• Languages: English
• ISSNs: 0146-6216

Abstract

This article focuses on four-parameter logistic (4PL) model as an extension of the usual three-parameter logistic (3PL) model with an upper asymptote possibly different from 1. For a given item with fixed item parameters, Lord derived the value of the latent ability level that maximizes the item information function under the 3PL model. The purpose of this article is to extend this result to the 4PL model. A generic and algebraic method is developed for that purpose. The result is practically illustrated by an example and several potential applications of this result are outlined.