Consider Exercise 15.6. Use a "+1" and "—1" scaling for '-high" and "low,'- respectively, and do a multiple linear regression with the model Y₁ = β₀ + β_1x1i + β₂x_2i + β₁₂x_1ix_2i + ε _i, with x u = reactant concentration (—1, +1) and x_2i = feed rate (-1, +1).

(a) Compute regression coefficients.

(b) How do the coefficients b₁, b₂, and b₁₂ relate to the effects you found in Exercise 15.6(a)?

(c) In your regression analysis do /-tests oil 61, b ₂. And b₁₂, how do these test results relate to those in Exercise 15.6(b) and (e :)?