Business statistics question?

Posted on 2016-04-05 18:55:00 in Statistics by SEFALI

AAA company has done extensive testing of it’s 1.5 volt D-size alkaline batteries by using them to continuously operate a standard flashlight and recording the time at which they fail. They found that this failure time is approximately normally distributed with a mean of 30 hours and a standard deviation of three hours. 

a) What is the probability that a battery of this type will have a failure time that exceeds 32 hours? 

b) What is the probability that a random sample of 25 such batteries will have a mean lifetime that exceeds 32 hours?

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