A national water expert is interested in determining the average amount of lead (in ppm, parts per million) that is found in the Houston, Texas drinking water. To conduct her research, she considers only those residential households within the city limits of Houston, Texas. She collects water samples from 1200 randomly selected households within the city limits to conduct her research.
a. Identify the population of interest to the water expert
b. Identify the sample of interest to the water expert
c. Identify the variable of interest to the water expert