The Lifetime (In Hours)of a 60-Watt Light Bulb Is a Random

question 70

Multiple Choice

The lifetime (in hours) of a 60-watt light bulb is a random variable that has a Normal distribution with  = 30 hours.A random sample of 25 bulbs put on test produced a sample mean lifetime of = 1038.Construct a 92% confidence interval estimate for the mean lifetime .If it were desired to cut the confidence interval to half its length while keeping the same 92% level,what size sample would be required to achieve this?

• A)50
• B)13
• C)75
• D)100
• E)41

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