(a)  A  random  sample  of  49  lunch  customers  was  taken  at  a  restaurant.  The  average  amount of time the customers in the sample stayed in the restaurant was 33 minutes. From  experience,  it  is  known  that  the  population  standard  deviation  equals  10  minutes.  Construct  a 95%  confidence  interval  for  the  true  mean  time  that  lunch  customers  stay  in  the  restaurant.   Interpret the result.    (b) How large of a sample would have to be taken so that the confidence interval estimate will be within 2.5 minutes with 95% confidence?

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A:

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