# Question

More light bulbs: Someone claims to have developed a new lightbulb whose mean lifetime is 1800 hours with a standard deviation of 100 hours. A sample of 100 of these bulbs is tested. The sample mean lifetime is 1770 hours.

a. If the claim is true, what is the probability of obtaining a sample mean that is less than or equal to 1770 hours?

b. If the claim is true, would it be unusual to obtain a sample mean that is less than or equal to 1770 hours?

a. If the claim is true, what is the probability of obtaining a sample mean that is less than or equal to 1770 hours?

b. If the claim is true, would it be unusual to obtain a sample mean that is less than or equal to 1770 hours?

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