irtlink

IRT Linking and Linking Error Estimation Across Time Points and Groups

irtlink uses unidimensional item response theory (IRT) models (1PL, 2PL, 3PL, and the partial credit and generalized partial credit models for polytomous items) to estimate trends in the mean and standard deviation of a latent ability distribution across time points of an educational assessment. It also estimates ability distribution differences across linked groups. Groups are connected through common items; their person samples may be independent, dependent, or drawn from different populations. The package quantifies the linking error induced by differential item functioning (DIF) in the estimates. For a tour of the package, see vignette("irtlink"), and for the function overview, see ?irtlink.

If you encounter a bug or have a suggestion, please open a GitHub issue or email me at engels@leibniz-ipn.de. The most useful reports contain a small example that reproduces the problem, including a minimal dataset (a sim_trend_data() call with a seed is usually sufficient), the shortest script that triggers the issue on that dataset, and the output of sessionInfo().

The version hosted here can be installed from within R using:

# install.packages("remotes")
remotes::install_github("oskarengels/irtlink")

or with devtools:

# install.packages("devtools")
devtools::install_github("oskarengels/irtlink")