# The customer care manager at a cell phone company

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1.The customer care manager at a cell phone company keeps track of how long each help-linecaller spends on hold before speaking to a customer service representative.He finds that thedistribution of wait times for all callers has a mean of 12 minutes with a standard deviation of5 minutes.The distribution is moderately skewed to the right.Suppose the manager takes arandom sample of 10 callers and calculates their mean wait time,.(a) What is the mean of the sampling distribution of?(b) Is it possible to calculate the standard deviation of?xIf it is, do the calculation.If it isn’t,explain why.(c) Do you know the approximate shape of the sampling distribution of?xIf so, describe theshape and justify your answer.If not, explain why not.xx
316The Practice of Statistics, 4/e- Chapter 7© 2011 BFW Publishers2.The weights of Granny Smith apples from a large orchard are Normally distributed with amean of 380 gm and a standard deviation of 28 gm.(a) A single apple is selected at random from this orchard.What is the probability that itweighs more 400 gm?(b) Three apples are selected at random from this orchard.What is the probability that theirmean weight is greater than 400 gm.?(c) Explain why the probabilities in (a) and (b) are not equal.
© 2011 BFW PublishersThe Practice of Statistics, 4/e- Chapter 7317Quiz 7.3BAP StatisticsName:1.The service department of a large automobile dealership keeps records of the odometerreadings of cars that it repairs and determines that the distribution of miles driven per year byall of its customers has a mean of 14,000 miles and a standard deviation of 4000.Thedistribution is skewed to the right. Suppose a random sample of 12 cars is taken from thehundreds of cars for which they have records, and mean number of miles per year,,xiscalculated.(a) What is the mean of the sampling distribution of?(b) Is it possible to calculate the standard deviation of?xIf it is, do the calculation.If itisn’t, explain why.(c) Do you know the approximate shape of the sampling distribution of?xIf so, describethe shape and justify your answer.If not, explain why not.x
318The Practice of Statistics, 4/e- Chapter 7© 2011 BFW Publishers2.The weights of newborn children in the United States vary according to the Normaldistribution with mean 7.5 pounds and standard deviation 1.25 pounds.The governmentclassifies a newborn as having low birth weight if the weight is less than 5.5 pounds.(a) What is the probability that a baby chosen at random weighs less than 5.5 pounds at birth?(b) You choose three babies at random and compute their mean weight,x.What is theprobability that their average birth weight is less than 5.5 pounds?(c) Explain why the probabilities in (a) and (b) are not equal.
© 2011 BFW PublishersThe Practice of Statistics, 4/e- Chapter 7319Quiz 7.3CAP StatisticsName:

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