IIF for 3PLM

Item Information Function for 3PLM

Usage

IIF3PLM(a, b, c, theta)

Arguments

a

slope parameter

b

location parameter

c

lower asymptote parameter

theta

ability parameter

Value

Returns a numeric vector representing the item information at each ability level theta. The information is calculated as: \(I(\theta) = \frac{a^2(1-P(\theta))(P(\theta)-c)^2}{(1-c)^2P(\theta)}\)

Note

This function will be removed in exametrika 3.0.0. It is a special case of ItemInformationFunc, which covers the 1PL to 4PL models; use that instead.