Refer to the Journal of Agricultural, Biological, and Environmental Statistics (March 2005) study of the chemical composition of rainwater, Exercise 12.1. Recall that the nitrate concentration, y (milligrams per liter), in a rainwater sample was modeled as a function of water source (groundwater, subsurface flow, or over ground flow).
a. Write a model for E(y) as a function of the qualitative independent variable.
b. Give an interpretation of each of the β parameters in the model, part c.

Data from Exercise 12.1

Researchers at the University of Aberdeen (Scotland) developed a statistical model for estimating the chemical composition of water (Journal of Agricultural, Biological, and Environmental Statistics, March 2005). For one application, the nitrate concentration (milligrams per liter) in a water sample collected after a heavy rainfall was modeled as a function of water source (groundwater, subsurface flow, or over ground flow).