The article “Arsenic and Mercury in Lake Whitefish and Burbot Near the Abandoned Giant Mine on Great SlaveLake” presents measurements of arsenic concentrations in fish found in Northern Canada.

a. In a sample of 8 whitefish caught in Yellowknife Bay, the mean arsenic concentration in the liver was 0.32 mg/kg, with a standard deviation of 0.05 mg/kg. Find a 95% confidence interval for the concentration in whitefish found in Yellowknife Bay.
b. In a sample of 8 whitefish caught in Baker Pond, the mean arsenic concentration in the liver was 0.55 mg/kg, with a standard deviation of 0.36 mg/kg. Should the Student’s t distribution be used to find a 95% confidence interval for the concentration in whitefish found in Baker Pond? If so, find the confidence interval. If not, explain why not.


(a)



(b) No. The minimum possible value is 0, which is less than two sample standard deviations below the sample mean. Therefore it is impossible to observe a value that is two or more sample standard deviations below the sample mean. This suggests that the sample may not come from a normal population.

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