Refer to the Environmental Science & Technology study of sorption of organic vapors, Exercise 12.7. Consider modeling the retention coefficient y as a function of both

x₁ = Temperature (degrees)

x₂ = Relative humidity (percent)

a. Write a first-order model for E(y).

b. Write a complete second-order model for E(y).

c. Write a model for E(y) that hypothesizes: (i) linear relationships, and (ii) that the relationship between retention (y) and temperature (x₁) depends on relative humidity (x₂).

Data from Exercise 12.7

Environmental Science & Technology (Oct. 1993) published an article that investigated the variables that affect the sorption of organic vapors on clay minerals. The independent variables and levels considered in the study are listed here. Identify the type (quantitative or qualitative) of each.