The accompanying data were obtained from a study of a certain method for preparing pure...

The accompanying data were obtained from a study of a certain method for preparing pure alcohol from refinery streams (“Direct Hydration of Olefins” Industrial and Engineering Chemistry [1961]: 209– 211). The independent variable x is volume, and the dependent variable y is amount of isobutylene converted.

Minitab output—the result of fitting a quadratic regression model where x₁ = x and x₂ = x²—is given. Would a linear regression have sufficed? That is, is the quadratic predictor important? Use a level .05 test.