The viscosity (y) of an oil was measured by a cone and plate viscometer at six different cone speeds (x). It was assumed that a quadratic regression model was appropriate, and the estimated regression function resulting from the observations was

a. Estimate , the expected viscosity when speed is 75 rpm.

b. What viscosity would you predict for a cone speed of 60 rpm?

c. If , and , compute and s.

d. From part (c), .

Using SSE computed in part (c), what is the computed value of R2

?

e. If the estimated standard deviation of is , test versus at level .01, and interpret the result.