A script for running a 2PL dichotomous item response theory analysis on the openly available LSAT data from ltm package in R

The script will let you output all parameter estimates for a 2PL or 3PL model and the following figures:

1. A scree-plot to check unidimensionality

2. Q3 statistic matrix to check for local dependence:

Example from this tutorial with no locally dependent items:

Example from another dataset with locally dependent items highlighted in blue and red:

3. Item Characteristic Curves:

Example from this tutorial:

Example from another dataset with variety of discriminability values:

4. Test/Item Characteristic Curves: