A company claims that the mean battery life of their MP3 player is 30 hours. You suspect the claim is incorrect and find that a random sample of 18 MP3 player has a mean battery life of 28.5 hours, and with a standard deviation of 1.7 hours. Using 1% level of significance, is there enough evidence to show that the true mean battery life is less than the claim?

What is the Null hypothesis (H0); Alternate hypothesis (H1); and the direction of the test?

Answers:

A) mu = 30, mu >30, left tailed test.

B) mu = 30, mu <30, left tailed test.

C) mu <= 30, mu > 30, right tailed test.

D) mu <= 30, mu >30, left tailed test.

Which distribution is used in this case?

What is the critical value?

What is the Test Statistic Value?

What is the P-value?

What is the conclusion of the test?