Elevated levels of mercury can cause hair loss, fatigue, and memory lapses. The concentration of mercury in a person’s blood can be greatly affected by diet, specifically, the amount of fish consumed....

Elevated levels of mercury can cause hair loss, fatigue, and memory lapses. The concentration of mercury in a person’s blood can be greatly affected by diet, specifically, the amount of fish consumed. Random samples of adults who eat fish two to three times per week and of adults who never eat fish were obtained. The mercury concentration in the blood of each person was measured (in micrograms per liter of blood), and the summary data are reported in the table below.

Assume both distributions are normal.

 a. Find a 95% confidence interval for the population mean mercury concentration in the blood of adults who eat fish regularly.

 b. Find a 95% confidence interval for the population mean mercury concentration in the blood of adults who never eat fish.

c. The safe level of mercury (set by the U.S. Environmental Protection Agency) is five micrograms per liter of blood. Is there any evidence to suggest either group is over the safe limit of mercury concentration?

 d. Use the confidence intervals in parts (a) and (b) to determine whether the two groups have different mean mercury concentration levels.