Three-Parameter Logistic Model

The three-parameter logistic model is a model where the lower asymptote parameter c is added to the 2PLM

Usage

ThreePLM(a, b, c, theta)

Arguments

a

slope parameter

b

location parameter

c

lower asymptote parameter

theta

ability parameter

Value

Returns a numeric vector of probabilities between c and 1, representing the probability of a correct response given the ability level theta. The probability is calculated using the formula: \(P(\theta) = c + \frac{1-c}{1 + e^{-a(\theta-b)}}\)

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.