Quiz 5 Stat 21

# Quiz 5 Stat 21 - students surveyed is small relative to the student population and there is no response bias 3 Is it reasonable to assume that

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Statistics 21: Quiz 5 Due: April 20, 2009 Name: Student ID: Instructions : Show your work – this means provide a formula, plug in the appropriate numbers, and then give a ﬁnal solution. It is good practice to attempt to complete the quiz in 50 minutes. Good luck! 1. When you play a number bet in roulette, you have a 1/38 chance of winning 35 dollars and a 37/38 chance of losing 1 dollar. If you play 100 independent number bets, approximate the chance that you will win more than 70 dollars in total. 2. You are interested in determining how many students at Public University have never cheated on a test. You conduct a random survey of 300 students and ﬁnd that 250 of them say they have never cheated on a test. Find a 95% conﬁdence interval for the proportion of students who have never cheated. (Assume the sample is a simple random sample, the number of
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Unformatted text preview: students surveyed is small relative to the student population, and there is no response bias.) 3. Is it reasonable to assume that there is no response bias when asking students if they have ever cheated on a test? Do you think the answers will be diﬀerent if the students answer a survey online or answer questions in person to an interviewer? 4. You have a box with 400 marbles in it. Your friend draws 100 marbles from the box with replacement and ﬁnds that 20 of them are red. He calculates that a 95% conﬁdence interval for the percentage of red marbles in the box is 12% - 28%. You know that the true percentage of red marbles is 29%. What did your friend do wrong? If he did nothing wrong, how do you explain the result?...
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## This note was uploaded on 07/08/2010 for the course STATS 21 taught by Professor Ibser during the Spring '09 term at University of California, Berkeley.

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