Draw appropriate summary graphs for the fitted model. If either of the quadratics or the interaction is unnecessary, drop it and refit before drawing graphs. (Data files: Forbes and Hooker) Refer to...

Draw appropriate summary graphs for the fitted model. If either of the quadratics or the interaction is unnecessary, drop it and refit before drawing graphs.

(Data files: Forbes and Hooker) Refer to the data in Assuming equal intercepts, obtain tests of equality of slopes for the two sources of observations. How does the test change if the suspected outlier in Forbes’s data, case 12, is removed?