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solprac1 - Practice Examination # 2 Sta 113: Probability...

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Practice Examination # 2 Sta 113: Probability and Statistics in Engineering October 25, 2006 This is a closed-book exam so do not refer to your notes, the text, or any other books (please put them on the Foor). You may use a single sheet of notes or formulas and a calculator, but materials may not be shared. Normal Z , student t , formula sheets, and three blank worksheets are attached to the exam. You must show your work to get partial credit. Even correct answers will not receive full credit without justi±cation. Please give all numerical answers to at least four correct digits or as exact fractions reduced to lowest terms. Write your solutions as clearly as possible and make sure it’s easy to ±nd your answers (circle them if necessary), since you will not receive credit for work that I cannot understand or ±nd. Good Luck! Cheating on exams is a breach of trust with classmates and faculty, and will not be tolerated. After completing the exam please acknowledge the Duke Honor Code with your signature below: I have neither given nor received unauthorized aid on this exam .
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Name: Sta 113 Problem 1 : Circle the best answer for each of parts 1–9: 1. A agricultural researcher plants 25 plots with a new variety of corn. A 90% conFdence interval for the average yield for these plots is found to be 162 . 72 ± 4 . 47 bushels per acre. Which of the following would pro- duce a conFdence interval with a smaller margin of error (i.e. shorter width) than this 90% conFdence interval? a) Plant only 5 plots rather than 25, because it is easier to control variability in 5 plots than in 25. b) Plant 100 plots rather than 25. c) Compute a 99% conFdence interval rather than a 90% conFdence interval. The increase in conFdence indicates that we have a better interval. d) None of the above.
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This note was uploaded on 01/17/2010 for the course STA 113 taught by Professor Staff during the Fall '08 term at Duke.

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solprac1 - Practice Examination # 2 Sta 113: Probability...

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