| estimate_impact | Estimate the effect size difference between focal and composite group abilities | 
| null_repsd | null_repsd | 
| plot_repsd | REPSD Null vs Observed Histogram | 
| repsd | repsd | 
| repsd_pval | Calculating p-values for repsd | 
| timmsData | Sample data from TIMMS | 
| timmsDiffic | Sample TIMMS item difficulties | 
| timmsDiscrim | Sample TIMMS item discriminations |