Chapter 4: Problem 5
Let \(X\) represent the difference between the number of heads and the number of tails obtained when a coin is tossed \(n\) times. What are the possible values of \(X ?\)
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Chapter 4: Problem 5
Let \(X\) represent the difference between the number of heads and the number of tails obtained when a coin is tossed \(n\) times. What are the possible values of \(X ?\)
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From a set of \(n\) randomly chosen people let \(E_{i j}\) denote the event that persons \(i\) and \(j\) have the same birthday. Assume that each person is equally likely to have any of the 365 days of the year as his or her birthday. Find (a) \(P\left(E_{3,4} \mid E_{1,2}\right)\); (b) \(P\left(E_{1,3} \mid E_{1,2}\right) ;\) (c) \(P\left(E_{2,3} \mid E_{1,2} \cap E_{1,3}\right)\). What can you conclude from the above about the independence of the \(\left(\begin{array}{l}n \\ 2\end{array}\right)\) events \(E_{i j} ?\)
A game popular in Nevada gambling casinos is Keno, which is played as follows: Twenty numbers are selected at random by the casino from the set of numbers 1 through 80. A player can select from 1 to 15 numbers; a win occurs if some fraction of the player's chosen subset matches with any of the 20 numbers drawn by the house. The payoff is a function of the number of elements in the player's selection and the number of matches. For instance, if the player selects only 1 number, then he or she wins if this number is among the set of 20 , and the payoff is \(\$ 2.2\) won for every dollar bet. (As the player's probability of winning in this case is \(\frac{1}{4}\), it is clear that the "fair" payoff should be \(\$ 3\) won for every \(\$ 1\) bet.) When the player selects 2 numbers, a payoff (of odds) of \(\$ 12\) won for every \(\$ 1\) bet is made when both numbers are among the 20 , (a) What would be the fair payoff in this case? Let \(P_{n, k}\) denote the probability that exactly \(k\) of the \(n\) numbers chosen by the player are among the 20 selected by the house. (b) Compute \(P_{n, k}\). (c) The most typical wager at Keno consists of selecting 10 numbers. For such a bet the casino pays off as shown in the following table. Compute the expected payoff:
Suppose that the number of accidents occurring on a highway each day is a Poisson random variable with parameter \(\lambda=3\). (a) Find the probability that 3 or more accidents occur today. (b) Repeat part (a) under the assumption that at least 1 accident occurs today.
Compare the Poisson approximation with the correct binomial probability for the following cases: (a) \(P\\{X=2\\}\) when \(n=8, p=.1\); (b) \(P\\{X=9\\}\) when \(n=10, p=.95\); (c) \(P\\{X=0\\}\) when \(n=10, p=.1\); (d) \(P\\{X=4\\}\) when \(n=9, p=.2\).
For a nonnegative integer-valued random variable \(N\), show that $$ E[N]=\sum_{i=1}^{\infty} P\\{N \geq i\\} $$
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