Use the Empirical Rule. The mean speed of a sample of vehicles along a stretch of highway is 64 miles per hour, with a standard deviation of 4 miles per hour. Estimate the percent of vehicles whose speeds are between 60 miles per hour and 68 miles per hour. (Assume the data set has a bell-shaped distribution.)
Approximately
% of vehicles travel between 60 miles per hour and 68 miles per hour