SOLUTION: Suppose the life of a particular brand of calculator battery is normally distributed with a mean of 80 hours and a standard deviation of 11 hours. a. what is the probability that

Question 874530: Suppose the life of a particular brand of calculator battery is normally distributed with a mean of 80 hours and a standard deviation of 11 hours.
a. what is the probability that a single battery randomly selected from the population will have a life of 75 to 85 hours? .3506
b. what is the probability that 9 randomly sampled batteries from the population will have a mean life of between 75 and 85 hours? .8274
c. if the manufacturer of the battery is able to reduce the standard deviation of battery life of 11 to 9 hours . what would be the probability that 9 batteries randomly sampled from the population will have a sample mean life of 75 and 85 hours?
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!
c. z = � 5/ (9/sqrt(9) = 5/3
.9522 - .0478
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