Ch07_Sect02_Keller MS_AISE TB

Ch07_Sect02_Keller MS_AISE TB - CHAPTER 7 SECTION 2: RANDOM...

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Unformatted text preview: CHAPTER 7 SECTION 2: RANDOM VARIABLES AND DISCRETE PROBABILITY DISTRIBUTIONS MULTIPLE CHOICE 68. 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. the average of the possible values of Y. ANS: B PTS: 1 REF: SECTION 7.2 69. A statistical measure of the strength of the relationship between two random variables X and Y is referred to as the: a. expected value b. variance c. covariance d. standard deviation ANS: C PTS: 1 REF: SECTION 7.2 70. 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 ANS: A PTS: 1 REF: SECTION 7.2 71. If X and Y are any random variables with E ( X ) = 5, E ( Y ) = 6, E ( XY ) = 21, V ( X ) = 9 and V ( Y ) = 10, then the relationship between X and Y is a: a. strong positive relationship b. strong negative relationship c. weak positive relationship d. weak negative relationship ANS: B PTS: 1 REF: SECTION 7.2 72. The covariance of two variables X and Y : a. must be between - 1 and +1. b. must be positive. c. can be any real number. d. None of these choices. ANS: C PTS: 1 REF: SECTION 7.2 73. If X and Y are any random variables with COV( X , Y ) = 0.25, , and , then the coefficient of correlation is a. 1.417 b. 1.190 c. 0.595 This edition is intended for use outside of the U.S. only, with content that may be different from the U.S. Edition. This may not be resold, copied, or distributed without the prior consent of the publisher. d. 0.354 ANS: C PTS: 1 REF: SECTION 7.2 74. If X and Y are independent random variables, which of the following identities is false? a. COV( X , Y ) = 1 b. E ( X + Y ) = E ( X ) + E ( Y ) c. V ( X + Y ) = V ( X ) + V ( Y ) d. All of these choices are true. ANS: A PTS: 1 REF: SECTION 7.2 TRUE/FALSE 75. Bivariate distributions provide probabilities of combinations of two variables. ANS: T PTS: 1 REF: SECTION 7.2 76. If X and Y are independent variables with V ( X ) = 23.48 and V ( Y ) = 36.52, then the standard deviation of W = X + Y is w = 7.746. ANS: T PTS: 1 REF: SECTION 7.2 77. If X and Y are independent variables, then COV( X , Y ) > 0. ANS: F PTS: 1 REF: SECTION 7.2 78. If X and Y are independent variables, then their coefficient of correlation = 0. ANS: T PTS: 1 REF: SECTION 7.2 79. If X and Y are two variables with , , and COV( X , Y ) = 11.76, then the coefficient of correlation = 0.8. ANS: T PTS: 1 REF: SECTION 7.2 80. If X and Y are two variables with E ( XY ) = 10.56, E ( X ) = 4.22, and E ( Y ) = 5.34, then COV( X , Y ) = 1.0. ANS: F PTS: 1 REF: SECTION 7.2 81. If X and Y are two variables with x = 3.8, y = 4.2, and COV( X , Y ) = - 0.25, then V ( X + Y ) = 31.58....
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This note was uploaded on 04/08/2012 for the course ADMS 2320 taught by Professor Rochon during the Spring '08 term at York University.

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Ch07_Sect02_Keller MS_AISE TB - CHAPTER 7 SECTION 2: RANDOM...

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