The data in the table on p. 624 were collected for a random sample of 26 households in Washington, D.C., during 2000. An economist wants to relate household food consumption, y, to household income, XI, and household size, x,, with the first-order model The SPSS printout for the model below is followed by several residual plots on pages 623 and 625.

a. Do you detect any signs of multicollinearity in the data' Explain.

b. Is there visual evidence that a second-order model may be more appropriate for predicting household food consumption? Explain.

c. Comment on the assumption of constant error vanance. Does it appear to be satisfied?