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Hypothesis test: Z test for Mean

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A light bulb manufacturer guarantees that the mean life of a certain type of light bulb is at least 925 hours. A random sample of 39 light bulbs has a mean life of 905 hours with a standard deviation o 55 hours. Do you have enough evidence to reject the manufacturer's claim? Use a=0.03.

a) Identify the null hypothesis and alternate hypothesis.

b) Identify the critical values.
Zo =

c) Identify the standardized test statistic.
Z =

d) Decide whether to reject or fail to reject the null hypothesis.

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Solution Summary

The solution provides step-by-step method for the calculation of testing of hypothesis using Z-test. 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.

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