In Exercise 6.1-7, lead concentrations near the San Diego Freeway in 1976 are given. During the fall of 1977, the weekday afternoon lead concentrations (in μg/m3) at the measurement station near the San Diego Freeway in Los Angeles were as follows:

(a) Construct a frequency distribution and display the results in the form of a histogram. Is this distribution symmetric?
(b) Calculate the sample mean and sample standard deviation.
(c) Locate , ± s on your histogram. How many observations lie within one standard deviation of the mean? How many lie within two standard deviations of the mean?
(d) Using the data from Exercise 6.1-7 and the data from this exercise, construct a back-to-back stem-and-leaf diagram with integer stems in the center and the leaves for 1976 going to the left and those for 1977 going to the right.
(e) Construct box-and-whisker displays of both sets of data on the same graph.

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