# Proportion and Standard Error

The Sony Corporation produces a Walkman that requires two AA batteries. The mean life of these batteries in this product is 35.0 hours. The distribution of the battery lives closely follows the normal probability distribution with a standard deviation of 5.5 hours. As a part of their testing program Sony tests samples of 25 batteries.

b. What is the standard error of the distribution of the sample mean? Use formula & show work.

c. What proportion of the samples will have a mean useful life of more than 36 hours? Use formula and show work.

d. What proportion of the sample will have a mean useful life greater than 34.5 hours? Use formula and show work.

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The proportion of the samples that will ...

#### Solution Summary

The solution provides step by step method for the calculation of standard error, test statistic, and proportion. Formula for the calculation and interpretations of the results are also included.