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Modeling Item Responses When Different Subjects Employ Different Solution Strategies

Mislevy, Robert J.; Verhelst, Norman
Publication Year:
Report Number:
ETS Research Report
Document Type:
Page Count:
Subject/Key Words:
Guessing (Tests), Item Response Theory (IRT), Models, Response Style (Tests), Test Taking Behavior


A model is presented for item responses when different examinees employ different strategies to arrive at their answers, and when only whose answers, not choice of strategy or subtask results, can be observed. Using substantive theory to differentiate the likelihoods of response vectors under a fixed set of solution strategies, we model responses in terms of item parameters associated with each strategy, proportions of the population employing each, and the distributions of examinee parameters within each. Posterior distributions can then by obtained for each examinees, giving the probabilities that they employe each of the strategies and their proficiency under each. The ideas are illustrated with a conceptual example about response strategies for spatial rotation items, and a numerical example resolving a population of examinees into subpopulations of valid responders and random guessers. (57pp.)

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