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exametrika (version 1.1.0)

IIF3PLM: IIF for 3PLM

Description

Item Information Function for 3PLM

Usage

IIF3PLM(a, b, c, theta)

Value

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

Arguments

a

slope parameter

b

location parameter

c

lower asymptote parameter

theta

ability parameter