# Normal Distribution and Sigma Calculations

Assume that the life in hours of a radio tube is normally distributed with mean 100 hours. If a purchaser requires at least 90 percent of them to have lives exceeding 80 hours, please show that the largest value that sigma can have and still have the purchaser satisfied is 15.6.

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Let X be the life of radio tube, then we want to find the largest sigma such ...

#### Solution Summary

This solution has step-by-step calculations to determine the largest value that sigma can be with the purchaser satisfied at 15.6.

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