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# Finding confidence Intervals for Toner

A manufacturer would like to estimate the average number of copies that can be made from a single bottle of toner. A random sample of 20 bottles was selected for this experiment. For the 20 bottles of toner the average number of pages was 1535 with a standard deviation of 50 pages.

a) Compute the 95% confidence interval for the average number of pages that can be made from a single bottle of toner. Interpret this interval.

b) How many bottles should be sampled in order to be 95% confident of being within 20 pages of the population mean number of pages per bottle?

#### Solution Preview

Please refer attached document for complete details. Work done with the help of equation writer may not print here.

Solution:

a)
Here n =sample size=20

Since sample size is less than 30, and population standard deviation is not known, we will use t statistics. First step will be to estimate the population standard deviation with sample standard deviation .i.e.

Estimated ...

#### Solution Summary

Solution describes the steps in finding out the confidence interval for number of pages a bottle of toner can copy. It also explains how to find out the sample size for given tolerance.

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