Question

A company has a policy of retiring company cars; this policy looks at number of miles driven, purpose of trips, style of car and other features. The distribution of the number of months in service for the fleet of cars is bell-shaped and has a mean of 40 months and a standard deviation of 6 months. Using the 68-95-99.7 rule, what is the approximate percentage of cars that remain in service between 28 and 34 months?

Answer 1

68–95–99.7 rule states that 68.27%, 95.45% and 99.73% of the values lie within one, two and three standard deviations of the mean, respectively.

The following information has been provided:

We need to compute

Using 68-95-99.7 rule

The corresponding z-values needed to be computed are:

Therefore, we get:

The following is obtained graphically:

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