The Rasch model, named for Georg Rasch, is a psychometric model for analyzing categorical data, such as answers to questions on a reading assessment or a questionnaire, as a function of the trade-off between a respondent's ability, attitude or personality trait and the difficulty of the item being answered, and it can be used, for example, to estimate a student's reading ability or the extremity of a person's attitude toward a topic from a set of questionnaire responses. Beyond psychometrics and educational research, the Rasch model and its extensions are also used in the health professions, agriculture and market research. The mathematics underlying the Rasch model is a special case of item response theory, but there are important differences in how its parameters are interpreted and in its philosophical implications, centered on specific objectivity, a defining property that Georg Rasch treated as a requirement for successful measurement, that separate proponents of the Rasch model from the broader item response modeling tradition.
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Core ClaimThe Rasch model, named after Georg Rasch, is a psychometric model for analyzing categorical data, such as answers to questions on a reading assessment or questionnaire responses, as a function of the trade-off between the respondent's abilities, attitudes, or personality traits, and the item difficulty. 1 FAQs
What does a 50 percent chance of a correct answer mean in the Rasch model?
A person has an even chance of answering correctly when their ability matches the item's difficulty.
In the Rasch model, the higher a person's ability is relative to the difficulty of an item, the higher the probability of a correct response on that item. When a person's location on the latent trait equals the difficulty of the item, the probability of a correct response is by definition 0.5. In other words, an item is as hard as the person is able when the person has an even chance of getting it right.
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1. Rasch model (Wikipedia)
WikipediaLead paragraph
The Rasch model, named after Georg Rasch, is a psychometric model for analyzing categorical data, such as answers to questions on a reading assessment or questionnaire responses, as a function of the trade-off between the respondent's abilities, attitudes, or personality traits, and the item difficulty.
References, Rasch's own 1960 work
Rasch, G. (1980) [1960]. Probabilistic models for some intelligence and attainment tests.
Developed By: Georg Rasch, Lead
The Rasch model, named after Georg Rasch, is a psychometric model for analyzing categorical data, such as answers to questions on a reading assessment or questionnaire responses, as a function of the trade-off between the respondent's abilities, attitudes, or personality traits, and the item difficulty.
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