A random sample of the houses in a particular city is selected and the level of radon gas is measured for each house in the sample. The values collected are given below in parts per million (ppm). Experience has shown that radon gas level is approximately normally distributed for this population.

Question

A random sample of the houses in a particular city is selected and the level of radon gas is measured for each house in the sample.  The values collected are given below in parts per million (ppm).   Experience has shown that radon gas level is approximately normally distributed for this population.
						4,  8,  13,  6,  7,  3,  9,  8,  11,  8

a)	Calculate a point estimate of the population mean of radon gas levels. (5 pts)

b)	Construct and interpret a 99% confidence interval for  . (6 pts)

c)  The city standards for radon call for no more than a level of 6 ppm.  From these data, does it appear that the mean radon level for city houses is under 6 ppm?  Provide statistical justification for your response. (2 pts)