SL: Stocking Lord Equating Procedure

In wasabi1989/MiscPsycho: Miscellaneous Psychometric Analyses

Description

This function estimates the A and B parameters (interept and slope) such that two tests with common items can be linked. Common items must be multiple choice items based on the 3-parameter logistic model.

Usage

SL(...)
## Default S3 method:
SL(params1, params2, con = 1e-3, ...)

Arguments

params1	item parameters of the common items used for linking organized as a list of lists for test A. See irt.ability for more details.
params2	item parameters of the common items used for linking organized as a list of lists for test B. See irt.ability for more details.
con	Criterion for convergence
...	a list of control parameters. These are actually passed from the function SLderivs, D a constant usually fixed at 1.7 to bring the logistic function into coincidence with the probit. mu mean of the normal prior distribution. sigma standard deviation of the normal prior distribution. Q number of quadrature points used in the Gauss-Hermite approximation.

Value

A list with class "SL" containing the following components:

A.Parameter	The Stocking-Lord intercept
B.Parameter	The Stocking-Lord slope
A Parameter	Mean/Sigma intercept used as the starting values
B Parameter	Mean/Sigma slope used as the starting values

Author(s)

Harold Doran

References

Kolen, M.J., Brennan, R.L. (2004). Test equating, scaling, and linking. Second Edition. Springer.

Examples

## This is 3PL and are values from page 171 of Kolen and Brennan
params1 <- list("3pl" = list(a = c(.4,1.7,1.2), b = c(-1.1, .9,2.2), c = c(.1,.2,.1)), "gpcm" = NULL)
params2 <- list("3pl" = list(a = c(.5,1.6,1), b = c(-1.5, .5,2), c = c(.1,.2,.1)), "gpcm" = NULL)
SL(params1, params2, control=list(Q=30, mu=0, sigma=1))

wasabi1989/MiscPsycho documentation built on Jan. 19, 2020, 12:29 a.m.