HW_2_Solution

HW_2_Solution - Homework #2 Solution BME 423 Fall 2008 1. (...

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Unformatted text preview: Homework #2 Solution BME 423 Fall 2008 1. ( pts) Null hypothesis: There is no statistically significant association between traveling abroad and being positive for P. alcalifaciens among people with gastroenteritis. Observed results: P. alcalifaciens Recent travel abroad? positive negative Total Surgical 25 229 254 Medical 5 368 373 Total 30 597 627 Expected contingency table if there is no difference between the travel abroad and not travel abroad: P. alcalifaciens Recent travel abroad? positive negative Total Surgical 12.15 241.85 254 Medical 17.85 355.15 373 Total 30 597 627 2 2 ( observed-expected 0.5) expected = 2 2 2 2 ( 25 12.15 0.5) ( 229 241.85 0.5) ( 5 17.85 0.5) ( 368 355.15 0.5) 12.15 241.85 17.85 355.15 = + + + 2 2 22.158 = (2 1) (2 1) 1 = = 2 2 0.05 22.158 (1) 3.841 = > = 2 2 0.001 22.158 (1) 10.828 = > = Conclusion: Reject null hypothesis. There is a statistically significant association between traveling abroad and being positive for P. alcalifaciens among people with gastroenteritis (p<0.001). 2. 2....
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This note was uploaded on 12/02/2008 for the course BME 423 taught by Professor D'argenio during the Fall '06 term at USC.

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HW_2_Solution - Homework #2 Solution BME 423 Fall 2008 1. (...

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