Question

When Easton runs the 400 meter dash, his finishing times are normally distributed with a mean of 80 seconds and a standard deviation of 3 seconds. Using the empirical rule, determine the interval of times that represents the middle 68% of his finishing times in the 400 meter race.

Answer 1

The empirical rule says about 68% of values lie within one standard deviation of the mean. So the interval is

80 ± 3 seconds → [77 seconds, 83 seconds].