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Unformatted text preview: ark of the College Entrance Examination Board. AP® Statistics 2000 ─ Scoring Guidelines Question 4 Solution a. part 1: States a correct pair of hypotheses Ho: µW = µN Ho: µW - µN = 0 OR Ha: µW ≠ µN Ha: µW - µN ≠ 0 where µW is the mean mental skill score for babies who used walkers and µN is the mean for those who did not. Nonstandard notation must be __ ∧ explained. Hypotheses about statistics (e.g. x or p ) are unacceptable. part 2: Identifies a correct test (by name or by formula), and checks appropriate assumptions. Note: Problem states that samples are random samples, so this does not need to be addressed in the assumptions. Independent samples t test. Assumptions: large sample or normal population distributions. Check: OK, because, for example, n1&n2>30. OR Pooled t test. Assumptions: large samples or normal population distributions, equal population standard deviations. Checks: OK because, for example, n1&n2>30 and s1≈s2. OR Independent samples z test. Assumptions: large samples. Check: OK because, for example, n1&n2>30. part 3: Correct mechanics, including value of test statistic, df (if appropriate), and Pvalue or rejection region (except for minor arithmetic errors) • For independent samples t test: __ t= __ xW − x N = 113 − 123 = − 10 = −3.8468 2 2 6.7576 12 2 15 2 sW s N + + 54 55 nW n N (Calculator: t = -3.846843677) df = 102.828 (OK to use 102), P-value = .0002 OR conservative df = 54 - 1 = 53, P-value = 2(.00016)=.00032 OR using tables (for either df) P-value < 2(.0005) = .001 • For pooled t test: sp = 13.597, t = -3.839, df = 107, P-value = .0002 (or < .001 from tables) • For independent samples z test, z = -3.8468, P-value = .0001 (or <2(.0002) = .0004 from tables) Copyright © 2000 College Entrance Examination Board and Educational Testing Service. All rights reserved. AP is a registered trademark of the College Entrance Examination Board. AP® Statistics 2000 ─ Scoring Guidelines Question 4 continued part 4: Stating a correct conclusion in the context of the problem, using the resu...
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This note was uploaded on 09/06/2013 for the course MATH AP Statist taught by Professor Mosby during the Spring '13 term at Silverton High School, Silverton.

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