Homework4 - 12 What is the probability of a score less than...

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Homework 4 In 2006, Apple’s market share for Macintosh computers jumped to 4.8% (we’ll assume everyone else owns a PC). We randomly sample 8 college freshmen to find out whether they use a Mac or a PC. 1. What is the probability that 5 of those freshmen use a Mac? 2. What is the probability that at least 6 freshmen use a Mac? 3. How many of those freshmen would we expect to use a PC? 4. What is the standard deviation for the number of people using a PC? On a given multiple choice test, there are 4 questions, each with 4 possible answers. Say you take the test by guessing randomly on each question. 5. How many questions would you expect to get right? 6. What’s the probability that you get all four questions correct? 7. What’s the probability that you get at least 2 questions correct? Use the normal probability table to help answer questions 9-17. 8. What is ] 23 . Pr[ - < Z ? 9. What is ] 91 . Pr[ > Z ? 10. What is ] 91 . 51 . Pr[ < < - Z ? IQ scores are normal with a mean of 100 and a standard deviation of 15. 11. What is the probability of a score greater than 110?
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Unformatted text preview: 12. What is the probability of a score less than 70? 13. What is the probability of a score between 70 and 115? A group of 9 people take an IQ test. 14. What is the probability that their average is greater than 93? 15. What is the probability that their average is less than 97? 16. What is the probability that their average is between 90 and 107? 17. What is the probability that their average is 100? 18. Let A and B be events such that Pr[ A ] = .5 and Pr[ B ] = 0.7. What must ] Pr[ B A ∩ equal for A and B to be independent? 19. Let A and B be events such that Pr[ A ] = .6, Pr[ B ] = .4, and ] Pr[ B A ∪ = .8. Are A and B independent? 20. Toss two dice and add the faces. What is the probability of a number greater than 7, given that one die is at least 4? 21. Toss two dice and add them. Let A be an event of an even number and let B be an event of a number less than 6. What are the elements of the intersection?...
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