The four-parameter logistic model is a model where one additional
parameter d, called the upper asymptote parameter, is added to the
3PLM.
Usage
LogisticModel(a = 1, b, c = 0, d = 1, theta)
Arguments
- a
slope parameter
- b
location parameter
- c
lower asymptote parameter
- d
upper asymptote parameter
- theta
ability parameter
Value
Returns a numeric vector of probabilities between c and d, representing
the probability of a correct response given the ability level theta. The probability
is calculated using the formula: \(P(\theta) = c + \frac{(d-c)}{1 + e^{-a(\theta-b)}}\)
