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 terf-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. Three of the variables are qualitative in nature: well class (public or private), aquifer (bedrock or unconsolidated), and detectible level of MTBE (below limit or detect). [A detectible level of MTBE occurs if the MTBE value exceeds .2 micrograms per liter.] The data for 11 selected wells are shown in the accompanying table.

a. Use graphical methods to describe each of the three qualitative variables for all 223 wells.
b. Use side-by-side bar charts to compare the proportions of contaminated wells for private and public well classes.
c. Use side-by-side bar charts to compare the proportions of contaminated wells for bedrock and unconsolidated aquifers.
d. What inferences can be made from the bar charts, parts a-c?

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Well Class Aquifer Detect MTBE Private Private Public Public Public Public Public Public Public Public Public Bedrock Bedrock Unconsolidated Unconsolidated Unconsolidated Unconsolidated Unconsolidated Unconsolidated Unconsolidated Bedrock Bedrock Below Limit Below Limit Detect Below Limit Below Limit Below Limit Detect Below Limit Below Limit Detect Detect