Effect of Item Response Theory (IRT) Model Selection on Testlet‐Based Test Equating. Issue 2 (13th August 2014)

• Record Type: Journal Article
• Authors: Cao, Yi; Lu, Ru; Tao, Wei
• Is Part Of: ETS research report series. Issue 2(2014:Dec.)
• Page Start: 1
• Page End: 13
• Publication Date: 2014-08-13
• Subjects: Testlet -- local item dependence -- dichotomous item response model -- polytomous item response model -- the testlet response model -- true score equating -- observed score equating; Universities and colleges -- Entrance examinations; Universities and colleges -- Graduate work -- Examinations; Universities and colleges -- United States -- Entrance examinations; Universities and colleges -- United States -- Graduate work -- Examinations; Graduate Record Examination; Educational tests and measurements; Social sciences; Education -- Research; Education -- Research; Educational tests and measurements; Graduate Record Examination; Social sciences; Universities and colleges -- Entrance examinations; Universities and colleges -- Graduate work -- Examinations; United States; 378
• DOI: 10.1002/ets2.12017
• Languages: English
• ISSNs: 2330-8516

Abstract

Abstract : The local item independence assumption underlying traditional item response theory (IRT) models is often not met for tests composed of testlets. There are 3 major approaches to addressing this issue: (a) ignore the violation and use a dichotomous IRT model (e.g., the 2‐parameter logistic [2PL] model), (b) combine the interdependent items to form a polytomous item and apply a polytomous IRT model (e.g., the graded response model [GRM]), and (c) apply a model that explicitly takes into account the dependence at the item level (e.g., the testlet response theory [TRT] model). In this study, a simulation was conducted to compare the performance of these 3 approaches on number‐correct score equating when degrees of testlet effect were manipulated. The traditional equipercentile method was used as an evaluation baseline. The results show that the 2PL and the TRT approaches produce comparable results that more closely agree with the results of the equipercentile method than the GRM does. And the number‐correct equating using the 2PL is robust to the violation of local item independence. Abstract : Report Number: ETS RR–14–19