ChainedLinearEquate: Apply chained linear equating

In CambridgeAssessmentResearch/KernEqWPS: Kernel Equating Without Pre-Smoothing

Apply chained linear equating

Description

Chained linear equating via an anchor test is done by successively applying the LinearEquate function between anchors and main tests.

Usage

ChainedLinearEquate(dx, dy)

Arguments

dx	Data frame with variables "x" and "a" representing scores for individual candidates on form X and on the anchor test.
dy	Data frame with variables "y" and "a" representing scores for individual candidates on form Y and on the anchor test.

Value

The function returns a list with the following elements:

chainedFunc

A function that translates any vector of scores on form X into equivalent scores on form Y.

EqTable

A data frame combining the sorted unique scores on form X in the data and their equated values on form Y.

Examples

#demonstrate method on a 30 item test with an internal 5 item anchor
#define 30 rasch item difficulties as equally spread
itedifs=rep(seq(-2,2,length=5),6)

#simulate population one item scores (and then form scores)
n1=300
t1=rnorm(n1,0.5,1)
ites1=0+(plogis(t1%*%t(rep(1,30))-rep(1,length(t1))%*%t(itedifs))>matrix(runif(n1*30),nrow=n1))
scoresX1=rowSums(ites1[,1:30])
scoresA1=rowSums(ites1[,26:30])
#simulate parallel tests in population two
n2=3000
t2=rnorm(n2,0,1)
ites2=0+(plogis(t2%*%t(rep(1,30))-rep(1,length(t2))%*%t(itedifs))>matrix(runif(n2*30),nrow=n2))
scoresY2=rowSums(ites2[,1:30])
scoresA2=rowSums(ites2[,26:30])

lin_eq=ChainedLinearEquate(data.frame(x=scoresX1,a=scoresA1),data.frame(y=scoresY2,a=scoresA2))
lin_eq

CambridgeAssessmentResearch/KernEqWPS documentation built on Feb. 23, 2024, 9:34 p.m.