Refer to the previous exercise. The means of percentage registered for the three categories are ¯x1 = 76.2,

¯x2 = 49.5, and ¯x3 = 39.7.

The overall mean ¯x = 60.4.

(a) Find the adjusted mean of the percentage voting for Anglos. Compare it to the unadjusted mean of 52.3, and interpret.

(b) Sketch a plot of the no-interaction model for these data, and identify on it the unadjusted and adjusted means for Anglos.