eatATA (version 1.1.2)

calculateIIF: Calculate Item Information Function

Description

Calculate item information function given item parameters of the 1PL, 2PL or 3PL IRT model.

Usage

calculateIIF(A = rep(1, length(B)), B, C = rep(0, length(B)), theta, D = 1.7)

Value

a matrix, with columns for different theta and rows for different items

Arguments

A

Vector of discrimination parameters.

B

Vector of difficulty parameters.

C

Vector of pseudo-guessing parameters.

theta

Vector of time intensity parameters.

D

the constant that should be used. Defaults to 1.7.

References

van der Linden, W. J. (2005). Linear models for optimal test design. New York, NY: Springer.

Examples

# TIF for a single item (2PL model)
calculateIIF(A = 0.8, B = 1.1, theta = 0)

# TIF for multiple items (1PL model)
calculateIIF(B = c(1.1, 0.8, 0.5), theta = 0)

# TIF for multiple theta-values (3PL model)
calculateIIF(B = -0.5, C = 0.25, theta = c(-1, 0, 1))

# TIF for multiple items and multiple ability levels (2PL model)
calculateIIF(A = c(0.7, 1.1, 0.8), B = c(1.1, 0.8, 0.5),
            theta = c(-1, 0, 1))