# Hypothesis Testing: Mean Lifetime of Light Bulbs

Hypothesis test for the population mean: Z test

A manufacturer claims that the mean lifetime, mu, of its light bulbs is 44 months. The standard deviation of these lifetimes is 8 months. Ninety bulbs are selected at random, and their mean lifetime is found to be 43 months. Can we conclude, at the 0.05 level of significance, that the mean lifetime of light bulbs made by this manufacturer differs from 44 months?

Perform a two-tailed test. Then fill in the table below.

Carry your intermediate computations to at least three decimal places, and round your responses as specified in the table.

The null hypothesis: Ho =

The alternative hypothesis: H1 =

The type of test statistic =

The value of the test statistic (round to at least 3 decimal places) =

The two critical values at the 0.05 level of significance (round to at least 3 decimal places) =

Can we conclude that the mean lifetime of the light bulbs made by this manufacturer differs from 44 months? _______

Please see attached file.

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#### Solution Summary

The solution provides step by step method for the calculation of testing of hypothesis. 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.