Question

The average life of light bulbs produced by SABA Electric Co. is expected to be normally distributed with the mean service life of 950 hours and standard deviation of 100 hours. A random sample of 100 bulbs is tested and it has a mean life of 910 hours. Can researcher conclude that the mean service life of the bulbs is less than the expectation? H0 is null hypothesis, and Ha is alternative hypothesis.

Which one of the following is a correct conclusion based on the given data?

Group of answer choices

Reject H0. The mean service life of the bulbs is less than the expectation.

Do not reject H0. The mean service life of the bulbs is less than the expectation.

Reject H0. The mean service life of the bulbs is not less than the expectation

Do not reject H0. The mean service life of the bulbs is not less than the expectation

None of the above.

Answer 1

Given:

= 950 hours, n = 100, = 910 hours, = 100 hours, = 0.05

Hypothesis:

Ho: = 950 hours

Ha: < 950 hours

Test statistic:

Critical value:

Z =Z0.05 = -1.645              ..................Using standard Normal table

Decision Rule:

Z < Z , Then Reject Ho at % level of significance.

Conclusion:

Z < Z , i.e. --4.0 < -1.645, That is Reject Ho at 5% level of significance.

We conclude that the mean service life of the bulbs is less than the expectation.

ANSWER: A

Reject H0. The mean service life of the bulbs is less than the expectation.