Use the Empirical Rule. The mean speed of a sample of vehicles along a stretch of highway is 69 miles per hour, with a standard deviation of 4 miles per hour. Estimate the percent of vehicles whose speeds are between 61 miles per hour and 77 miles per hour.
(Assume the data set has a bell-shaped distribution.)
Approximately
% of vehicles travel between 61 miles per hour and 77 miles per hour.