Question

a) An industrial product is shipped in lots of 15 items. Testing to determine whether an item is defective is costly, and hence the manufacturer samples his production rather than inspecting each item. A sampling plan is devised and calls for sampling five items from each lot. If the lot contains four defectives, what is the probability that exactly two defectives are found in this sample?

b)

You run into your long lost relative at the airport, but you have to dash off to catch your connecting flight (so quickly you can’t type on your phone). You ask your relative for their phone number, and they tell you verbally their ten digit phone number. You remember the first six digits perfectly, but for the last digits! You are certain that the last four digits involved the numbers 1,3,8,7,0, or 4 each occurring at most once. How many possible phone numbers are there for your long lost relative?

Answer 1