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Sample Size

Operators are to answer telephone calls from customers in an average time of 0.1 minute or less, and either respond to or refer to the proper department within 0.5 minute. Estimate the actual overall time for both components, in total. A pilot study sample of 30 actual operator times was drawn, with the results in following table.

Component Mean time Standard deviation
Answer 0.1023 0.0183
Service 0.5290 0.0902

If the manager wants to be 95 percent confident that the overall time is correctly estimated, with a 3% probability of error, what size sample should be taken?

P bar is .5, alpha is .95, E is .03

Solution Summary

The solution provides step by step method for the calculation of sample size. Formula for the calculation and Interpretations of the results are also included. Interactive excel sheet is included. The user can edit the inputs and obtain the complete results for a new set of data.