The data below are 30 waiting times between eruptions of the Old Faithful geyser in Yellowstone National Park.

a. Calculate the range.
b. Use the range approximation to approximate the standard deviation of these 30 measurements.
c. Calculate the sample standard deviation s.
d. What proportion of the measurements lie within two standard deviations of the mean? Within three standard deviations of the mean? Do these proportions agree with the proportions given in Tchebysheff's Theorem?

56 89 51 79 58 82 52 88 5278 69 75 77 72 71 55 87 53 85 61 93 54 76 80 81 59 86 78 71 77