155S4.2.notebook
January 27, 2010
MAT 155­DY1 & DY2
Section 4.2 Fundamentals of Probability
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155S4.2.notebook
January 27, 2010
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155S4.2.notebook
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Section 4­2 Fundamentals of Probability 154/3. A news reporter states that a particular event is unusual because its probability is only 0.001. Is that correct statement? Why or why not?
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155S4.2.notebook
January 27, 2010
Section 4­2 Fundamentals of Probability 154/4. Use subjective judgment to estimate the probability that the next time you ride an elevator, it gets stuck between floors.
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155S4.2.notebook
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Section 4­2 Fundamentals of Probability 155/8. Identify Probability Values.
(a) Certain event
(b) Impossible event
(c) Sample space of 10 equally likely events. Probability of each.
(d) True/false test. Probability of guessing correctly.
(e) Multiple­choice test with 5 possible answers. Guess correctly.
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Section 4­2 Fundamentals of Probability 155/10. In a study of 420,095 cell phone users in Denmark, it was found that 135 developed cancer. Estimate the probability that a randomly selected cell phone user will develop such cancer. Is the result very different from the probability of 0.000340 that was found for the general population? What does the result suggest about cell phones as a cause of such cancer?
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155S4.2.notebook
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Section 4­2 Fundamentals of Probability 156/16. NYC has 750 pedestrian walk buttons that work and 2500 that do not work. Select one at random. Probability it works?
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155S4.2.notebook
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Section 4­2 Fundamentals of Probability 156/18. For 1733 trials, the IRS was correct 1107 times and wrong 626 times.
(a) Estimate the probability that a randomly selected taxpayer’s question will be answered incorrectly.
(b) Is it unusual for IRS to provide a wrong answer to a taxpayer’s question? Should it be unusual?
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155S4.2.notebook
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Section 4­2 Fundamentals of Probability 157/24. Table 4­1 shows of 122 subjects who used marijuana the test was wrong 3 times. (a) Find the probability of a wrong test result for a person who does use marijuana.
(b) Is it “unusual” for the test result to be wrong for those?
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155S4.2.notebook
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Section 4­2 Fundamentals of Probability 157/26. Both parents have the brown/blue pair of eye color genes, and each parent contributes one gene to a child. Assume that if the child has at least one brown gene, that color will dominate and the eyes will be brown.
(a) List the different possible outcomes. Assume that these outcomes are equally likely.
(b) What is the probability that a child of these parents will have the blue/blue pair of genes?
(c) What is the probability that the child will have brown eyes?
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155S4.2.notebook
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Section 4­2 Fundamentals of Probability 158/30. The probability of the horse Outta Here winning the 129th Kentucky Derby was 1/50. What were the actual odds against Outta Here winning that race?
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Section 4­2 Fundamentals of Probability 158/32. A $2 bet that Funny Cide would win resulted in a return of $27.60
(a) How much profit from a $2 bet?
(b) Payoff odds against a Funny Cide win?
(c) If Funny Cide has a 2/33 probability of winning, what are actual odds against his winning?
(d) If payoff odds in (c) were actual odds, how much would a $2 ticket be worth after the Funny Cide win?
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