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August 2, 2015

Homework Help: Stats

Posted by Ryan on Monday, January 31, 2011 at 3:45am.

The distribution of lifetimes for a particular brand of lightbulbs has a mean of 110 hours and a standard deviation of 20 hours. Suppose a random sample of 35 lightbulbs is taken for observation.

What is the probability that the sample mean lifetime will be between 105 and 115 hours?


0.4306

0.3026

0.1974

0.7372

0.8612

What value does the sample mean exceed with 95% probability (Hint: This is the 5th percentile for the sample mean distribution)?


77.10

106.79

104.44

116.63

115.56

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