A new light bulb is being considered for use in an office with computers. It is decided that the new bulb will only be used if it has a mean lifetime of more than 500 hours. A random sample of 40 bulbs is selected and placed on life test. The mean and standard deviation are found to be 505 hours and 18 hours, respectively. Use a 0.01 level of significance.

The hypothesis to be tested is:

H0: mu=500 vs. Ha: mu>500

The test statistic is:

z=1.76

Please state the correct conclusion.

A.

Accept the null hypothesis.

B.

Not enough information is given.

C.

Fail to reject the null hypothesis.

D.

Reject the null hypothesis.