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Some Supporting Evidence for Lord's Guideline for Estimating "c" IRT

Author(s):
Thissen, David; Wainer, Howard
Publication Year:
1985
Report Number:
RR-85-15, PSRTR-85-57
Source:
ETS Research Report
Document Type:
Report
Page Count:
5
Subject/Key Words:
Item Response Theory (IRT), Lord, Frederic M., Statistical Analysis, Testing Problems

Abstract

The estimation of the height of the lower asympote "c" of the item characteristic curve is sometimes very difficult. The inaccurate estimation of "c" becomes a more serious concern because of the substantial covariance between "c" and the item difficulty "b". This paper deals with the different schemes suggested to alleviate this problem. (5pp.)

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