11.49. Ify = 2 + 3x| + 5x2 - 8x3, then controlling for X2 and X3, the predicted mean change in y when xi is increased from 10 to 20 equals

(a) 3 (b)30 (c)0.3

(d) Cannot be given—depends on specific values ofX2 and X3.

11.50. Ify = 2 + 3xi + 5x2 - 8x3,

(a) The strongest correlation is between y and X3.

(b) The variable with the strongest partial influence on y isx2.

(c) The variable with the strongest partial influence on y is X3, but one cannot tell from this equation which pair has the strongest correlation.

(d) None of the above.