Hexavalent chromium has been identified as an inhalation carcinogen and an air toxin of...

Hexavalent chromium has been identified as an inhalation carcinogen and an air toxin of concern in a number of different locales. The article “Airborne Hexavalent Chromium in Southwestern Ontario” (J. of Air and Waste Mgmnt. Assoc., 1997: 905–910) gave the accompanying data on both indoor and outdoor concentration (nanograms/m³) for a sample of houses selected from a certain region.

a. Calculate a confidence interval for the population mean difference between indoor and outdoor concentrations using a confidence level of 95%, and interpret the resulting interval.

b. If a 34th house were to be randomly selected from the population, between what values would you predict the difference in concentrations to lie?