Question

At a local restaurant, the amount of time that customers have to wait for their food is normally distributed with a mean of 18 minutes and a standard deviation of 3 minutes. Using the empirical rule, what percentage of customers have to wait between 12 minutes and 24 minutes?

Answer 1

12 and 24 are 18 ± 6, i.e. μ ± 2σ. By the empirical (68–95–99.7) rule about 95% of values lie within two standard deviations, so about 95% (≈95.45% exactly) of customers.