The concentration of mercury in a lake has been monitored for a number of years. Measure...

The concentration of mercury in a lake has been monitored for a number of years. Measurements taken on a weekly basis yielded an average of (milligrams per cubic meter) with a standard deviation of . Following an accident at a smelter on the shore of the lake, 15 measurements produced the following mercury concentrations.

a. Give a point estimate of the mean mercury concentration after the accident.

b. Construct a 95% confidence interval on the mean mercury concentration after the accident. Interpret this interval.

c. Is there sufficient evidence that the mean mercury concentration has increased since the accident? Use α = .05.

d. Assuming that the standard deviation of the mercury concentration is , calculate the power of the test to detect mercury concentrations of 1.28, 1.32, 1.36,and 1.40.