Arsenic in groundwater. Refer to the Environmental

QUESTION:

Problem 45E

Arsenic in groundwater. Refer to the Environmental Science& Technology (Jan. 2005) study of the reliability of a commercial kit to test for arsenic in groundwater, Exercise 12.16(p. 682). Recall that you fit a first-order model for arsenic level(y) as a function of latitude (x1), longitude (x2), and depth (x3).

a. Write a model for arsenic level (y) that includes firstorder terms for latitude, longitude, and depth, as wellas terms for interaction between latitude and depth andinteraction between longitude and depth.

b. Use statistical software to fit the interaction model, part a,to the data. Give the least squares prediction equation.

c. Conduct a test (at α = .05) to determine whether latitude and depth interact to affect arsenic level.

d. Conduct a test (at α = .05) to determine whether longitude and depth interact to affect arsenic level.

e. Practically interpret the results of the tests, parts c and d.