# midterm2 - Stat 2103 Midterm Exam 2 April 5th NAME 25...

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Stat 2103, Midterm Exam 2 April 5th. NAME: 25 points total. You can use the distribution tables, a calculator, and a one-page formula sheet. Problem 1-2. A discrete random variable x can assume possible values 2, 3, 4, and 5. Its probability distribution is shown below. x 2 3 4 5 p ( x ) 0.125 0.375 ? 0.125 1. What is p ( x 4)? a. 0.125; b. 0.25; c. 0.5; d. 0.875. Answer: D 2. Calculate the expected value. a. 3.5; b. 2.5; c. 3; d. 2. Answer: A 3. The ages of a group of 50 men are approximately normal with mean 28 years and a variance of 4 years. For a randomly selected man from this group, the probability of his age falls between 24 and 26 is a. -0.1359; b. 0.1359; c. 0.1499; d. -0.1499. Answer: B 4. The chances of a tax return being audited are 10 in 1000 if an income is less than \$100 , 000 and 30 in 1000 if an income is \$100 , 000 or more. If four taxpayers with incomes under \$100 , 000 are randomly selected, what is the probability that at most one will be audited? a. 0.999; b. 0.001; c. 0.961; d. 0.039. Answer: A Problem 5-6. The number of semester hours of college credit taken by first- time candidates for a certain professional exam has a distribution with a mean of 134 hours and a standard deviation of 14 hours. Consider a random sample of 100 first-time candidates for the exam and let ¯ x represent the mean number of hours of college credit taken for the sample.

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