Chapter 4.1, Problem 42E

(a)

To determine

To explain what “ ${95}^{th}$ percentile” means in this setting.

Explanation of Solution

Some internet service providers (ISPs) charge companies based on how much bandwidth they use in a month. Thus we need to find what the ${95}^{th}$ percentile means in this context.

This means that the ${95}^{th}$ percentile is the bandwidth for which the company uses less than this bandwidth $95\%$ of the time. The company uses a bandwidth smaller than the ${95}^{th}$ percentile $95\%$ of the time.

(b)

To determine

To explain is it possible or not to determine the z -score for a usage total that is at the ${95}^{th}$ percentile and if it is so then find the z -score.

Answer to Problem 42E

  ${98}^{th}$ percentile.

Explanation of Solution

It is possible to determine the z -score for a usage total that is at the ${95}^{th}$ percentile. And the z -score for the bandwidth will be ${98}^{th}$ percentile, because the bandwidth will be higher for the ${98}^{th}$ percentile than for the ${95}^{th}$ percentile and a higher bandwidth will cost more. Hence, the result.