Chapter 1.4, Problem 15E

An urn contains ten red and ten white balls. The balls are drawn from the urn at random, one at a time. Find the probabilities that the fourth white ball is the fourth, fifth, sixth, or seventh ball drawn if the sampling is done

(a) With replacement.

(b) Without replacement.

(c) In the World Series, the American League (red) and National League (white) teams play until one team wins four games. Do you think that the urn model presented in this exercise could be used to describe the probabilities of a four-, five-, six-, or seven-game series’? (Note that either red” or white” could win.) If your answer is yes, would you choose sampling with or without replacement in your model? (For your information, the numbers of four-, five-, six-, and seven-game series, up to and including 2017, were 21. 25. 24.39. This ignores games that ended in a tie, which occurred in 1907, 1912, and 1922. Also, it does not include the 1903 and 1919—1921 series, in which the winner had to take five out of nine games. The World Series was canceled in 1994.)