LogisticModel {exametrika}R Documentation

Four-Parameter Logistic Model

Description

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)}}


[Package exametrika version 1.1.0 Index]