Rasch measurement model

Definition

Group of mathematical models for relating and predicting the individual’s score on a test item to his level of performance on a scale of the ability or trait being measured, and the item’s difficulty parameter. The Rasch model considers that the probability of an individual to provide the right answer or to perform efficiently a given task only depends on the difference between his level of ability and the level of item difficulty. This probability increases when the ability is higher than the item difficulty, but is 50% if these two parameters are equal.