Refer to Exercise 6.9.
a. Based on the values of the sample mean and sample standard deviation for magnesium, provide a reason why the distribution of magnesium does not have a normal distribution.
b. Are the inferences given in Exercise 6.9 valid based on your answer in part (a)?
The study of concentrations of atmospheric trace metals in isolated areas of the world has received considerable attention because of the concern that humans might somehow alter the climate of the earth by changing the amount and distribution of trace metals in the atmosphere. Consider a study at the South Pole, where, over a 2-month period, seventy air samples were obtained. In thirty-five of the samples, the amount of magnesium was determined. In the remaining thirty-five samples, the amount of europium was determined.
a. What are the populations of interest in this study?
b. Is there significant evidence of a difference in the mean magnesium and Europium levels? Use a 5 .05.
c. What is the level of significance of your test?
d. Estimate the mean levels of magnesium and Europium using a 95% confidence interval.