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Unformatted text preview: STA 3024 Homework 2 Section 7459 Form B Name: UFID: This form is only for students whose UFID number begins with 0, 4, 5, or 9. Answer all problems neatly . If you turn in more than one piece of paper, they must be stapled . Work that isn’t neat or stapled may lose points. You don’t need to turn in this problem listing, but you do need to include your name , UF-ID number , and form code on your homework. For each of the following problems, do the following: • State the best type of inference method to use (from the ones covered in the Review 2 slides on the website). • State the assumptions and whether or not they are satisfied. Irrespective of whether or not you think they are satisfied, perform the analysis. The only assumption you may assume true if not stated is randomization. • Perform a hypothesis test, stating the assumptions, test-statistic value, p-value, and conclusion. Inter- pret the conclusion in the context of the problem. • If we went over a confidence interval corresponding to the method you chose, make the 95% confidence interval. Interpet it in the context of the problem. State whether or not you reach the same conclusion from the hypothesis test as the confidence interval. 3 problems × 12 points 2 problems × 4 points (2 points for right method, 2 points completion) 44 points total 1. total points: 12 In the first week of January 2012, CBS conducted a poll which asked 1,247 people if they would vote for President Barack Obama or Governor Rick Perry; 42% responded in favor of Governor Perry. In mid-December, CNN/Opinion Research conducted a similar poll asking 1,015 people the same question; 37% responded in favor of Governor Perry. Is there evidence that Governor Perry’s support has increased from December to January? Best Inference Method 2 points Two sample proportions (independent groups) Assumptions 2 points • Data obtained from randomization • Two independent groups • Categorical response variable for the two groups • Large enough sample sizes (at least 10 “successes” and 10 “failures” in each group) They are all clearly met. 1 Hypotheses 2 points H : p 1- p 2 = 0 vs. H A : p 1- p 2 > Hypothesis Test First note the following: 1 = 0 . 42 n 1 = 1247 2 = 0 . 37 n 2 = 1015 = . 42(1247) + 0 . 37(1015) 1247 + 1015 = 0 . 398 2 points So, we compute z = . 42- . 37 q . 398(1- . 398) ( 1 1247 + 1 1015 ) = 2 . 41 2 points This gives usa right-tailed p-value of 1-.9920=0.008, which is far less thanThis gives usa right-tailed p-value of 1-....
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This note was uploaded on 02/14/2012 for the course STA 3024 taught by Professor Ta during the Spring '08 term at University of Florida.
- Spring '08