A new light bulb is being considered for use in an office with computers. It is

Question

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:
Ho: mu=500 vs Ha: mu>500
The test statistic is: z=1.76

Please state the correct conclusion
A. Accept the null hypothesis
B. Reject the null hypothesis
C. Not enough information is given
D. Fail to reject the null hypothesis

Explanation / Answer

p-value applicable to right tailed test = P(Z > z)
= P(Z > 1.76)
= 0.0392
Since p-value (0.0392) > the alpha value (0.01), it can be said that there is NO evidence to reject the Ho
Therefore, CHOICE (B) Fail to reject the null hypothesis is the answer...

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