Referring to the earthquake data in Exercise 2.20,
(a) Find the sample mean and standard deviation.
(b) What proportion of these observations lies between x ± 2 s?

Data from in Exercise 2.20

In a recent year, 35 sites around the world experienced earthquakes of magnitude greater than 6.5.

Construct a histogram using equal-length intervals starting with (6.5, 6.8 ], where the right-hand endpoint is included but not the left-hand endpoint.

6.6 6.6 6.6 6.6 6.6 6.6 6.7 6.7 6.7 6.8 6.9 6.9 6.9 6.9 7.0 7.0 7.0 7.0 7.1 7.1 7.1 7.2 7.2 6.7 6.7 6.8 6.8 7.5 7.6 7.7 7.8 7.8 7.8 7.9 7.9