IPW.MLMPN               Estimating the treatment effect from a
                        partially nested design with the
                        inverse-propensity-weighted multilevel modeling
                        estimation approach
IPW.meandifference      Estimating the treatment effect from a
                        partially nested design using the
                        inverse-propensity-weighted mean difference
                        estimation approach
dat_obs                 Observed data in a partially nested design.
