CalculateItemDifferences: Calculates the differences between two item option...

Description Usage Arguments Value Author(s)

View source: R/NCDIF.R

Description

Calculates the differences between two item option characteristic curves for all options (minus one).

Usage

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CalculateItemDifferences(thetaValue, itemParameters, irtModel = "2pl",
  logistic = TRUE)

Arguments

thetaValue

A numeric value or array for the theta (ability) value(s) for which the difference will be calculated

itemParameters

A list containing "focal" and "reference" item parameters. Item parameters are assumed to be on the same scale. Item parameters for each group should me a matrix with nrow equal to the number of items.

irtModel

A string stating the irtModel to be used. Should be one of "1pl", "2pl", "3pl", "grm" or "pcm".

logistic

A logical value stating if the IRT model will use the logistic or the normal metric.

Value

difference A numeric matrix with the differences on probabilities or on expected score for each item between focal and reference groups.

Author(s)

Victor H. Cervantes <vhcervantesb at unal.edu.co>


DFIT documentation built on May 29, 2017, 10:31 p.m.