Fit of Responses to the Model IV—Guessing

Abstract

In the 3PThree-parameter (3P) modelmodel, a guessing parameterGuessing parameteris estimated for each item, in addition to parameters for the item’s location and discrimination. The Rasch model makes no provision for guessing behaviour. Therefore, guessing affects item and person estimates. A person is most likely to show guessing if an item is very difficult for the person. Guessing can be diagnosed with the Rasch model, by removing the responses that have a high chance of being guessed because they are too difficult. The analysis of the modified matrix is referred to as a tailored analysisTailored analysis.