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Chapter 6: Q.75 (page 403)
Blood types In the United States, of adults have type O blood. Suppose we choose U.S. adults at random. Let the number who have type O blood. Use the binomial probability formula to find . Interpret this result in context.
The chance of out of people with O blood type is .
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A large auto dealership keeps track of sales and leases agreements made during each hour of the day. Let = the number of cars sold and = the number of cars leased during the 铿乺st hour of business on a randomly selected Friday. Based on previous records, the probability distributions of and are as follows:
顿别铿乶别 .
Find and interpret .
85. Aircraft engines Engineers define reliability as the probability that an item will perform its function under specific conditions for a specific period of time. A certain model of aircraft engine is designed so that each engine has probability of performing properly for an hour of flight. Company engineers test an SRS of engines of this model. Let the number that operate for an hour without failure.
(a) Explain why is a binomial random variable.
(b) Find the mean and standard deviation of. Interpret each value in context.
(c) Two engines failed the test. Are you convinced that this model of engine is less reliable than it鈥檚 supposed to be? Compute and use the result to justify your answer.
Better readers?() Did students have higher reading scores after participating in the chess program? Give appropriate statistical evidence to support your answer.
Exercises 47 and 48 refer to the following setting. Two independent random variables and have the probability distributions, means, and standard deviations shown.
48. Difference Let the random variable .
(a) Find all possible values of D. Compute the probability that takes each of these values. Summarize the probability distribution of in a table.
(b) Show that the mean of is equal to.
(c) Confirm that the variance of is equal to .Find all possible values of . Compute the probability that takes each of these values. Summarize the probability distribution of in a table.
A large auto dealership keeps track of sales made during each hour of the day. Let = the number of cars sold during the 铿乺st hour of business on a randomly selected Friday. Based on previous records, the probability distribution of is as follows:
The random variable has mean and standard deviation .
To encourage customers to buy cars on Friday mornings, the manager spends to provide coffee and doughnuts. The manager鈥檚 net pro铿乼 on a randomly selected Friday is the bonus earned minus this . Find the mean and standard deviation of.
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