The two-parameter logistic model is a classic model that defines the probability of a student with ability theta successfully answering item j, using both a slope parameter and a location parameter.
Value
Returns a numeric vector of probabilities between 0 and 1, representing the probability of a correct response given the ability level theta. The probability is calculated using the formula: \(P(\theta) = \frac{1}{1 + e^{-a(\theta-b)}}\)
Note
This function will be removed in exametrika 3.0.0. It is a special case of LogisticModel, which covers the 1PL to 4PL models; use that instead.