Figure 1.

Visual tests of the underlying assumptions. Five concentration ellipses for (a) the standardized mac1 dataset and (b) for a Monte Carlo simulated dataset with the same parameters of location and variance-covariance matrix (we used robust versions the location and scale estimators) as in mac1 data. The tolerance ellipses cover 90% (red), 95% (blue), 99% (green), 99.9% (orange) and 99.99% (light orange) portions of the standard normal distribution to assist in visually testing the assumption of contaminated bivariate normality. QQNP of residuals for (c) mac1 dataset and (d) for the corresponding Monte Carlo simulated dataset for comparison with (a) and (b). Outlying points are given in different colors in accordance with STIs in Figure 19b.