Output Values

• Empirical quantile-quantile plot: This graph plots covariate values that fall in (approximately) the same quantile of treated and control distributions. Control unit quantile values are plotted on the x-axis, and treated unit quantile values are plotted on the y-axis. If values fall below the 45 degree line, control units generally take lower values of the covariate. Data points that fall exactly on the 45 degree line indicate that the marginal distributions are identical.

• Jitter plots: This graph plots jittered estimated propensity scores of treated and control units. Dark diamonds indicate matched units and grey diamonds indicate unmatched or discarded units. The area of the diamond is proportional to the weights. Vertical lines are plotted if subclassification is used.

• Histograms: This graph plots histograms of the estimated propensity scores in the original treated and control groups and weighted histograms of the estimated propensity scores in the matched treated and control groups. Plots can be compared vertically to quickly check the balance before and after matching.