scoreCon {MiscPsycho}R Documentation

Function to create a score conversion table from Rasch item parameters

Description

Creates a score conversion table using the estimated item parameters

Usage

scoreCon(b_vector)
## Default S3 method:
scoreCon(b_vector)

Arguments

b_vector vector of estimated item parameters

Value

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

Estimate the maximum likelihood estimate (MLE, or ability estimate) conditional on the item parameters
Std.Error the estimated standard error of the ability estimate
Raw.Score the associated raw test score. Since Rasch does not use pattern scoring, all raw scores have the same MLE.

Note

Scores cannot be provided for individuals with 0 correct or all incorrect because the likelihood function is unbounded in these cases. Other scoring methods, such as the EAP or MAP are available for these scenarios. See irt.ability for more general scoring methods

Author(s)

Harold Doran

Examples

set.seed(1234)
tmp <- data.frame(item1 = sample(c(0,1), 20, replace=TRUE), item2 = sample(c(0,1), 20, replace=TRUE),
item3 = sample(c(0,1), 20, replace=TRUE),item4 = sample(c(0,1), 20, replace=TRUE),item5 = sample(c(0,1), 20, replace=TRUE))

## Estimate item parameters from JML (or provide them as a numeric vector)
fm1 <- jml(~ item1 + item2 + item3 + item4 + item5, data = tmp)
summary(scoreCon(coef(fm1)))

[Package MiscPsycho version 1.5 Index]