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Unformatted text preview: bulb tested; the third bulb tested; the fourth bulb tested. 6. A fair coin is tossed six times. Given that there are at least three heads, what is the probability that there are exactly four heads? 7. Billy, Silly, and Nilly shoot at a bulls eye. They can hit the bulls eye 70, 80, and 75% of the times, respectively. One of the three is known to have hit the eye. Find the probability that it was Nilly. 8. The scores of students in a standardized exam are normally distributed with mean 500 and standard deviation 100. (a) Jolly scored 654; what is her percentile score? (b) Billy scored 540; what is his percentile score? (c) Molly is at the 95th percentile of the score distribution; what is Mollys score? 9. A normally distributed random variable has mean 40 and the probability that it is between 20 and 60 is 0.5. What is its variance? 1...
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 Spring '08
 Staff
 Statistics

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