5.61) Priority Mail is the U.S. Postal Service’salternative to commercial expres

Question

5.61) Priority Mail is the U.S. Postal Service’salternative to commercial express mail companies such as FEDEX. Anarticles in the Wall Street Journal presented some interestingconclusions comparing Priority Mail shipments with the much lessexpensive first-class shipments. When comparing shipments intendedfor delivery in three days, first class deliveries failed todeliver on time 19% of the time, whereas Priority Mail failed 33%of the time. Note that at the time of the articles, first-classdeliveries started as low as $0.34 and Priority mail started at$3.50.

If 10 items are to be shipped first-class to 10 differentdestinations claimed to be in a three-day delivery location, whatis the probability that

A)   0 items will take more than three days?

B)    Exactly 1 item will take more then threedays?

C)    2 or more will take more then threedays?

D)   What are the mean and the standard deviation ofthe probability distribution?

Explanation / Answer

Mine is correct because "2 or more" means we want k = 2,3,4,....10  and it means we DONT want  k = 0 or 1.  The other poster subtracted out k = 2, which is not correct.

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