Ch07 - CHAPTER 7 RANDOM VARIABLES AND DISCRETE PROBABILTY...

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Unformatted text preview: CHAPTER 7 RANDOM VARIABLES AND DISCRETE PROBABILTY DISTRIBUTIONS MULTIPLE CHOICE QUESTIONS In the following multiple-choice questions, please circle the correct answer. 1. The weighted average of the possible values that a random variable X can assume, where the weights are the probabilities of occurrence of those values, is referred to as the: a. variance b. standard deviation c. expected value d. covariance ANSWER: c 2. The number of accidents that occur annually on a busy stretch of highway is an example of: a. a discrete random variable b. a continuous random variable c. a discrete probability distribution d. a continuous probability distribution ANSWER: a 3. A function or rule that assigns a numerical value to each simple event of an experiment is called: a. a sample space b. a probability tree c. a probability distribution d. a random variable ANSWER: d 94 95 Chapter Seven 4. If X and Y are any random variables, which of the following identities is not always true? a. E ( X + Y ) = E ( X ) + E ( Y ) b. V ( X + Y ) = V ( X ) + V ( Y ) c. E (4 X +5 Y ) = 4 E ( X ) + 5 E ( Y ) d. V (4 X +5 Y ) = 16 V ( X ) + 25 V ( Y ) + 40 COV ( X , Y ) ANSWER: b 5. If X and Y are random variables, the sum of all the conditional probabilities of X given a specific value of Y will always be: a. 0.0 b. 1.0 c. the average of the possible values of X d. a value larger than zero but smaller than 1.0 ANSWER: b 6. A statistical measure of the strength of the linear relationship between two random variables X and Y is referred to as the: a. expected value b. variance c. covariance d. standard deviation ANSWER: c 7. A table, formula, or graph that shows all possible values a random variable can assume, together with their associated probabilities is called a: a. discrete probability distribution b. continuous probability distribution c. bivariate probability distribution d. probability tree ANSWER: a 8. If X and Y are random variables with E ( X ) = 5 and E ( Y ) = 8, then E (2 X +3 Y ) is: a. 34 b. 13 c. 18 d. 40 ANSWER: a 9. If X and Y are random variables with V ( X ) = 7.5, V ( Y ) = 6 and COV ( X , Y ) = 4, then V (2 X +3 Y ) is: a. 33 b. 37 c. 88 Random Variables and Discrete Probability Distributions 96 d. 132 ANSWER: d 10. If X and Y are independent random variables, which of the following identities is always true?...
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Ch07 - CHAPTER 7 RANDOM VARIABLES AND DISCRETE PROBABILTY...

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