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Flag 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. On using the appropriate test of hypothesis to determine whether the new bulb should be used at 0.01 level of significance, the rejection region of the test is O z> 2.33 O 2