The polynomial response model adopted for the 1981 soybean data did not use the O 3 quadratic × SO 2 linear interaction term but the text suggested that it would be the next most logical term to test....

The polynomial response model adopted for the 1981 soybean data did not use the O₃
quadratic × SO₂
linear interaction term but the text suggested that it would be the next most logical term to test. Add the term X²
₁X₂
to the model shown in equation 16.4 and fit the 1981 soybean. Compare these results to those obtained from the model shown in equation 16.4 and test the significance of the new term. State your conclusions.