Lead concentrations (ppm) at two background and four compliance wells (four monthly samples for each well).
A data frame with 24 observations on the following 4 variables.
Lead concentrations (ppm)
a factor indicating the month of collection
a factor indicating the well number
a factor indicating the well type (background vs. compliance)
USEPA. (1989b). Statistical Analysis of Ground-Water Monitoring Data at RCRA Facilities, Interim Final Guidance. EPA/530-SW-89-026. Office of Solid Waste, U.S. Environmental Protection Agency, Washington, D.C. p.5-23.