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Question: The mean life span of an electric bulb is 350 hours, with a standard deviation of 10 hours. A random sample 40 of a particular brand of electric bulbs is taken and found that their mean life span was 348 hours. State the null hypothesis( Ho) for the situation.


A ) Ho: The mean life span of the bulbs = 400
B ) Ho: The mean life span of the bulbs = 300
C ) Ho: The mean life span of the bulbs = 450
D ) Ho: The mean life span of the bulbs = 350

Steps to derive

1 Ho: The mean life span of the bulbs = 350 hours.



Hence the right answer is Option D

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