Stt practice exam2

# Stt practice exam2 - Review Questions for Exam 2/lectures...

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Review Questions for Exam 2/lectures 01 and 06/spring 08/Dikong 1. The baseball World Series ends when a team wins 4 games. Suppose that sports analysts consider one team a bit stronger, with a 55% chance to win any individual game. Find the probability that the underdog will win the series by winning the first 4 games. a. .0915 b. .450 c. .0410 d .550 e. .239 2.3. A commuter must pass through 5 traffic lights on her way to work each day, stopping for red lights. She estimates the probability of stopping from 0 to 5 times as follows: x = #red 0 1 2 3 4 5 P(X = x) .05 .25 .35 .15 .15 .05 2. How many lights should she expect to stop for? a. 2.25 b. 2.5 c. 1.0 d. 2.33 e. Not enough information to answer 3.What is the standard deviation? a. 2.50 b. 1.59 c. 1.00 d. 1.26 e. None of these 4-5 A gambler places one \$20 bet on 3 football games and has a 50% chance of winning his bet on each game. The bookie keeps his \$20. The gambler is paid later as follows, depending on the number of winners he picked: 0 \$0 1 \$0 2 \$25 3 \$50 4. What is his expected gain? Remember, a loss is a negative gain, and that the bookie keeps the gambler’s \$20! a. -\$20 b. 15.625 c. \$0 d. -\$4.375 e. -\$8.7 5. What is the standard deviation of his gain? a. 302 b. 20 c. 17.4 d. 22.3 e. None of these 6-11. An Olympic archer is able to hit the bull’s eye 90% of the time. Assume each shot is independent of the others. If she shoots 5 arrows, what’s the probability of each result described below. 6. Her first bull’s eye comes on the third arrow. (a) 0.729 (b) 0.009 (c) 0.081 (d) None of these

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7. She misses the bull’s eye at least once. (a) 0.41 (b) 0.59 (c) 0.99 (d) None of these 8. She gets exactly 4 bull’s eye. (a) 0.066 (b) .005 ( c) 0.328 (d) None of these 9. She gets atleast 4 bull’s eye. (a) 0.328 (b) 0.918 (c) 0.009 (d) 0.59 10. Find the mean of the number of bull’s eye she may get. (a) 4.5 (b) 10 (c) 3 (d) 0.67 11. Find the standard deviation of the numbers of bull’s eye she may get. (a)0.45 (b) 4.5 (c) 0.67 (d) 3 Problems 12 – 13: A statistics professor thinks that grading tests takes too long, so he adopts a new rule: He grades problems in a random order. If the student gets the first problem wrong, she gets a grade of zero. If she gets the first problem right but the second one wrong, her grade is 1.0. This scale continues; a student’s grade is the number of problems she gets right before getting one wrong. Students getting more than 4 problems right simply get extra credit. The professor stops grading when he finds an incorrect problem. The test has many problems. 12. If a student can do 80% of all problems, what is the chance that she will get a grade of 2.0 or higher? a.
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Stt practice exam2 - Review Questions for Exam 2/lectures...

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