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Unformatted text preview: STAT 420 Spring 2009 Version A Name ANSWERS . Exam 2 Page Possible Earned 1 9 2 9 3 3 4 9 5 9 6 10 7 11 Total 60 Be sure to show all your work; your partial credit might depend on it. No credit will be given without supporting work. The exam is closed book and closed notes. You are allowed to use a calculator and one 8½" x 11" sheet with notes on it. ___________________________________________________________________________ Academic Integrity The University statement on your obligation to maintain academic integrity is: If you engage in an act of academic dishonesty, you become liable to severe disciplinary action. Such acts include cheating; falsification or invention of information or citation in an academic endeavor; helping or attempting to help others commit academic infractions; plagiarism; offering bribes, favors, or threats; academic interference; computer related infractions; and failure to comply with research regulations. Rule 33 of the Code of Policies and Regulations Applying to All Students gives complete details of rules governing academic integrity for all students. You are responsible for knowing and abiding by these rules. 1. A society of bird watchers has collected data from several towns on stork sighting ( x ) and human births ( y ) to test the widely expressed belief that storks bring babies. Assume that ( X , Y ) have a bivariate normal distribution. The data are given in the table below: Storks, x 18 16 10 20 14 26 22 Babies, y 27 15 13 21 19 39 27 Σ x = 126, Σ y = 161, Σ x 2 = 2,436, Σ y 2 = 4,175, Σ x y = 3,150, Σ ( x – x ) 2 = 168, Σ ( y – y ) 2 = 472, Σ ( x – x ) ( y – y ) = Σ ( x – x ) y = 252. a) (7) Test H : ρ = 0 vs. H a : ρ > 0 at the α = 0.10 level of significance. What is the pvalue of the test? (You can give a range.) ( 29 ( 29 ( 29 ( 29 472 168 252 2 2 = = ∑ ∑ ∑ y y x x y y x x r ≈ 0.8949 ....
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This note was uploaded on 04/27/2009 for the course STAT 420 taught by Professor Stepanov during the Spring '08 term at University of Illinois at Urbana–Champaign.
 Spring '08
 STEPANOV
 Statistics

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