Refer to the Environmental Science & Technology (Jan. 2005) study of methyl tert-butyl ether (MTBE) contamination in New Hampshire wells, Exercise 2.12. Data collected for a sample of 223 wells are saved in the MTBE file. Recall that each well was classified according to well class (public or private), aquifer (bedrock or unconsolidated), and detectable level of MTBE (below limit or detect).
a. Consider an experiment in which the well class, aquifer, and detectable MTBE level of a well are observed. List the simple events for this experiment. (Hint: One simple event is Private/Bedrock/Below Limit.)
b. Use statistical software to find the number of the 223 wells in each simple event outcome. Then, use this information to compute probabilities for the simple events.
c. Find and interpret the probability that a well has a detectable level of MTBE.
Data from Exercise 2.12
In New Hampshire, about half the counties mandate the use of reformulated gasoline. This has led to an increase in the contamination of groundwater with methyl tert-butyl ether (MTBE). Environmental Science & Technology (Jan. 2005) reported on the factors related to MTBE contamination in public and private New Hampshire wells. Data were collected for a sample of 223 wells. These data are saved in the MTBE file. Three of the variables are qualitative in nature: well class (public or private), aquifer (bedrock or unconsolidated), and detectable level of MTBE (below limit or detect). (Note: A detectable level of MTBE occurs if the MTBE value exceeds .2 micrograms per liter.) The data for 10 selected wells are shown in the accompanying table.
