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Some Standard Errors in Item Response Theory IRT

Wainer, Howard
Publication Year:
Report Number:
ETS Research Report
Document Type:
Page Count:
Subject/Key Words:
Equated Scores, Error of Measurement, Item Response Theory (IRT), Mathematical Models, Test Theory, Testing Problems


The mathematics required to calculate the asymptotic standard errors of the parameters of three commonly used logistic item response models is described and used to generate values for some common situations. It is shown that the maximum likelihood estimation of a lower asymptote can wreak havoc with the accuracy of estimation of a location parameter, indicating that if one needs to have accurate estimates of location parameters (say for purposes of test linking/equating or computerized adaptive testing) the sample sizes required for acceptable accuracy may be inadequate for maximum likelihood estimation in most applications. It is suggested that other estimation methods be used if the three parameter model is applied in these situations. (29pp.)

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