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Unformatted text preview: Stat 145: Exam 3 Review Answers 1. (a) The probability is: P ( X < 15) = P X- 31 . 8 10 < 15- 31 . 8 10 = P ( Z <- 1 . 68) = . 0465 (b) The mean of the sampling distribution is 31.8 and the standard deviation is: σ √ n = 10 √ 25 = 2 (c) Yes, the sampling distribution of ¯ X is approximately Normal because the popu- lation distribution is approximately Normal. (d) The probability is: P ( ¯ X > 35) = P ¯ X- 31 . 8 2 > 35- 31 . 8 2 = P ( Z > 1 . 6) = 1- . 9452 = . 0548 2. (a) You must check two things: • Are all probabilities between 0 and 1? Yes. • Do the probabilities sum to 1? Yes. . 000 + 0 . 003 + 0 . 060 + 0 . 062 + 0 . 036 + 0 . 121 + 0 . 691 + 0 . 027 = 1 (b) The probability is 0 . 000 + 0 . 003 + 0 . 060 + 0 . 062 = 0 . 125. (c) The probability is 1- . 691 = 0 . 309. 3. The population is all adult residents in Albuquerque. The parameter is the percentage of adult residents in Albuquerque who favor the mayor’s proposal. The sample is the 900 adult residents randomly chosen. The statistic is 40%.900 adult residents randomly chosen....
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