# Mean Lifetime of Light Bulbs

A manufacturer claims that the mean lifetime of its light bulbs is 51 months. The standard deviation of these lifetimes is 5 months. Fifty bulbs are selected at random, and their mean lifetime is found to be 50 months. Can we conclude....(see attached)

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#### Solution Summary

A manufacturer claims that the mean lifetime, , of its light bulbs is months. The standard deviation of these lifetimes is months. Fifty bulbs are selected at random, and their mean lifetime is found to be months. Can we conclude, at the level of significance, that the mean lifetime of light bulbs made by this manufacturer differs from 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: H : ____

0

The alternative hypothesis: H : _____

1

The type of statistic: a. Z

b. t

c. Chi square

d. F

The value of the test statistic: ______

(Round your answer to at least

three decimal places.)

The two critical values at the 0.1 level of significance: _____

(Round your answer to at least

three decimal places.)

Can we conclude that the mean lifetime of light bulbs made by this manufacturer differs from 51 months? Yes or No?