addDiscriminationIndex: Calculate Conventional Item Discrimination Index

Description Usage Arguments References

Description

Calculates the conventional item discrimination index, based on complete test results only. Follows the formulation described in Lopez (1998), where item discrimination d = p(UG) - p(LG). UG and LG are the upper and lower groups – the upper and lower 27% of students as ranked by their overall test scores – and p(UG) and p(LG) are the proportion of correct answers in each group.

Usage

1
addDiscriminationIndex(mctd, percentile = 0.27)

Arguments

mctd

Existing mcTestAnalysis data object

percentile

Percentile defining upper and lower groups (standard is 0.27)

References

The Item Discrimination Index: Does it Work? Tristan Lopez A. Rasch Measurement Transactions, 1998, 12:1 p. 626. http://www.rasch.org/rmt/rmt121r.htm


gadenbuie/mctestanalysis documentation built on May 16, 2019, 5:34 p.m.