man/README.md

In MontclairML/ctticc: Item characteristic curve estimation from classical test theory indices

ctticc

Item characteristic curves (ICC's) are visual indicators of important attributes of assessment items - most commonly difficulty and discrimination. Assessment specialists who examine ICC's usually do so from within the psychometric framework of either Item Response Theory (IRT) or Rasch modeling. This R package provides an extension of this tradition into the Classical Test Theory (CTT) framework. The package has a psych dependency that facilitate the estimation of CTT-generated difficulty (pseudob) and discrimination (pseudoa) "parameters" from a psych::alpha object, and then plots the ICCs.

A handy compilation of how to interpret IRT parameters is located here.

| Quick Links | |:-------| | How to Use | | Plot Screenshots | | Future Advancements |

How to Use

To install from GitHub use devtools::install_github("MontclairML/ctticc").

Next, load the package via library(ctticc)

The function specification is:

ctticc(dataframe, items, plot, nrow, ncol)

The dataframe should contain binary responses from all items comprising the unidimensional scale. If you have additional information in your dataframe (e.g., respondent identifiers, demographics, or variables unrelated to the unidimensional scale), use square brackets [] to identify your test items.

The items field indicates which columns should be presented visually. Use the concatenate function if you'd like to specify non-sequential items (for example, c(1,4,7)) would present ICCs for data columns 1, 4, and 7.

plot has values of grid, separate, or together. If using the grid specification, you will also need to specify nrow and ncol (for example, the grid screenshot reflects values of 3 and 2).

Plot Screenshots

| separate | grid | together | |:---------------:|:---------------------:|:---------------------:| | | |

Future Advancements

We may add a "pseudo" Test Information Function. Please also give us feedback and requests for additions or changes.

MontclairML/ctticc documentation built on April 14, 2025, 7:33 a.m.