Calculates Raju's Signed Area Measure index for an item with given item parameters of focal and reference groups.

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Description

Calculates Raju's Signed Area Measure index for an item with given item parameters of focal and reference groups.

Usage

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SignedArea(itemParameters, irtModel = "2pl", subdivisions = 5000,
  logistic = TRUE)

Arguments

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".

subdivisions

A numeric value indicating the number of subdivisions for numerical integration.

logistic

A logical value stating if the IRT model will use the logistic or the normal metric. Defaults to using the logistic metric by fixing the D constant to 1. If FALSE the constant is set to 1.702 so that the normal metric is used.

Value

sam A numeric matrix with the Signed Area Measure values for all the item parameter in each set of itemParameterList

Author(s)

Victor H. Cervantes <vcervantes at icfes.gov.co> <vhcervantesb at unal.edu.co>

References

Cohen, A., Kim, S-H and Baker , F. (1993). Detection of differential item functioning in the Graded Response Moodel. Applied psychological measurement, 17(4), 335-350

Raju, N. (1988). The area between two item characteristic cureves. Psychometricka, 53(4), 495–502.

Examples

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data(dichotomousItemParameters)
sam3pl <- SignedArea(itemParameters = dichotomousItemParameters, irtModel = "3pl",
                     subdivisions = 5000, logistic = TRUE)

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