Homework#8 - Dre? a. 10% b. 90% c. 97.72% d. 2.28% e. None...

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Stat 133 Autumn 2007 NAME Allison Heck Homework #8 (10 points) GROUP #___________ Due Tuesday Nov. 20 (at or before the beginning of recitation) Use the following information for all questions on this homework: Exam scores in Bob’s Stat 133 class have a normal distribution with mean 80 and standard deviation 5. (Scores are out of a total of 100 points.) 1. Bob’s exam score was at the 70 th percentile. That means he scored 70 points on the exam. a. TRUE b. FALSE 2. Arun’s exam score was two standard deviations above the mean. What was Arun’s exam score? a. 82 b. 90 c. Between 70 and 90 d. None of the above 3. Dre’s exam score was 90. What percentage of students in the class scored lower than
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Unformatted text preview: Dre? a. 10% b. 90% c. 97.72% d. 2.28% e. None of the above 4. Select one student at random from Bobs class. What is the chance that his/her score will be higher than 78? (Show all work and put your final answer in the blank.) z = (78 80)/5 = - .40 1-.3446 = .6554 ANS 65.54% 5. Take a random sample of 49 students from Bobs class and find their average score. What is the chance that their average score will be higher than 78? (Show all work and put your final answer in the blank.) 1 P(x-bar < 78) = 1 P(z < (78-80)/(5/7)) = 1 P(z < -2.8) = 1 - .0026 = .9974 ANS 99.74%...
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