Talk:Rasch model

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What about the contributions done by Erling B. Andersen?

psychometrika Volume 71, Number 1 / March, 2006

[edit] dichotomous data

"In general, the probability of a person responding correctly to a question with difficulty lower than that person's location is greater than 0.5, while the probability of responding correctly to a question with difficulty greater than the person's location is less than 0.5"

dichotomous is two choices, right? how can the probability fall below .5? surely no test is designed so that an ignorant choice scores less than random choice? am I missing something?

a dichotomous variable can take on two values; e.g. 0,1. when people mark something correct or incorrect the score is a dichotomous variable. an example is a mathematics problem - there are many ways to get it wrong but (often) only one way to get it right, and the score of 0 or 1 is used to denote an incorrect or correct response. the dichotomy is right vs wrong. dichotomous does not imply two choices are available to a respondent in a multiple choice format. Holon 11:31, 2 May 2007 (UTC)