| add_spl_est | The additive spline estimator | 
| aipwee_est | Prediction with a residual bias correction estimator | 
| bart_est | The BART estimator | 
| gam_est | The GAM estimator | 
| get_ci | This calculates an upper and lower bound from bootstrap matrix | 
| hi_est | The Hirano and Imbens estimator | 
| hi_sim_data | Simulated data from Hirano and Imbens (2004) | 
| iptw_est | The inverse probability of treatment weighting (iptw) estimator | 
| ismw_est | The inverse second moment weighting (ismw) estimator | 
| iw_est | The inverse weighting estimator (nonparametric method) | 
| nmes_data | Data set containing data from the National Medical Expenditure Survey (NMES) | 
| nw_est | The Nadaraya-Watson modified estimator | 
| overlap_fun | This function creates an overlapping dataset | 
| prop_spline_est | The propensity-spline prediction estimator | 
| reg_est | The regression prediction estimator | 
| scalar_wts | This function calculates scalar weights for use in other models | 
| sim_data | Simulated data from Schafer and Galagate (2015) | 
| t_mod | A function to estimate conditional expected values and higher order moments | 
| wtrg_est | The weighted regression estimator |