solfinalS09

# solfinalS09 - PSTAT 120C Outline of Solutions to the Final...

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Unformatted text preview: PSTAT 120C: Outline of Solutions to the Final Exam Questions June 10, 2009 1. (a) Fill in this table of expected values under the assumption of independent rows and columns: Angels No Angels Don’t Know Total Aliens 26.1 10.4 23.6 60 No Aliens 46.9 18.6 42.4 108 Total 73 29 66 168 (8) (b) The χ 2 statistic is X 2 = 0 . 59 + 1 . 09 + 0 . 01 + 0 . 33 + 0 . 60 + 0 . 01 = 2 . 64 (8) (4) (c) The critical value for a χ 2 2 is 5.99. Therefore, we conclude that there is not enough evidence to reject the null hypothesis that these two answers are independent. (8) 2. (a) The Mann–Whitney U statistic is 2 because only 0.169 is more than 2 of the New obser- vations. The rank-sum statistic is 12 and U = 12- 10 = 2. (8) (b) From the table in the back of the book, P { U ≤ 2 } = 0 . 019. This is a one-sided test so the P = 0 . 019. (4) (c) We would conclude that there is a statistically significant improvement in using the New software because 0 . 019 ≤ . 05....
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solfinalS09 - PSTAT 120C Outline of Solutions to the Final...

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