In the model E(y) = + 1x + 2x2, the coefficient 2 (a) Is the mean

In the model E(y) = α + β1x + β2x2, the coefficient

β2

(a) Is the mean change in y as x2 is increased one unit with x held constant.

(b) Is a curvature coefficient that describes whether the regression equation is bowl shaped or mound shaped.

(c) Equals 0 if the relationship between y and x is linear.

(d) Equals 0 if the population value of R2 for this model equals ρ2 yx.