A researcher is wanting to study the reliability of a commercial kit to test for arsenic in groundwater. The data is attatched.
a) Write a model for arsenic level that includes first-order terms for latitude (x1), longitude (x2), and depth (x3), as well as terms for interaction between latitude and depth, and interaction between longitude and depth.
b) Use staistical software to fit the interaction model, part a, to the data in the file. Give the least squares prediction equation.
c) Conduct a test (at alpha = .05) to determine whether latitude and depth interact to effect arsenic level.
d) Conduct a test (same alpha) to determine whether longitude and depth interact to effect arsenic level
e) Practically interpret the results of parts c and d