During 2012, Texas had listed on FracFocus, and industry tracking disclosure site, nearly 6000 oil and gas wells in which the fracking methodology was use to extract natural gas. Fontenot et al. (2013) reports on a study of 100 private water wells in or near the Barnett Shales in Texas. There were 91 private wells located within 5 km of an active gas well using fracking, 4 private wells with no gas wells located within a 14 km radius, and 5 wells outside of the Barnett Shale with no gas well located with a 60 km radius. They found that there were elevated levels of potential contaminants such as arsenic and selenium in the 91 wells closest to natural gas extraction sites compared to the 9 wells that were at least 14 km away from an active gas well using the fracking technique to extract natural gas.

Four part question. Answer all parts.

(a) Identify the population that is of interest to the researchers.

(b) Describe the sample.

(c) What characteristics of the population are of interest to the researchers?

(d) If the sample measurements are used to make inferences about the population characteristics, why is a measure of reliability of the inferences important?