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solutionset11

# solutionset11 - Problem Set 11 Solutions STAT 3022 section...

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Unformatted text preview: Problem Set 11 Solutions STAT 3022, section 001 12/06/2011 18.17. Alcohol and Breast Cancer. Breast cancer Cases Controls Totals Fewer than 4 drinks per week 330 658 988 4 or more drinks per week 204 386 590 Totals 534 1044 1578 Wish to test H : π 2- π 1 = 0 vs. H a : π 2- π 1 > • Sample proportions of breast cancer: ˆ π 1 = 330 988 = 0 . 33401 , ˆ π 2 = 204 590 = 0 . 34576 • Difference: ˆ π 2- ˆ π 1 = . 01175 • Proportion from combined sample: ˆ π c = 330 + 204 988 + 590 = 0 . 33840 • Normal approximation is OK. • Standard error (test version): SE(ˆ π 2- ˆ π 1 ) = r (0 . 33840)(0 . 66160) 988 + (0 . 33840)(0 . 66160) 590 = . 02462 • z-statistic: z = . 01175 . 02462 = . 477 • p-value: P ( Z > . 477) = . 317 • Conclusion : There is no evidence that the two proportions differ. > prop.test(c(330,204),c(988,590),corr=F,alternative="less") 2-sample test for equality of proportions without continuity correction data: c(330, 204) out of c(988, 590) X-squared = 0.228, df = 1, p-value = 0.3165 alternative hypothesis: less 95 percent confidence interval:-1.00000000 0.02882218 sample estimates: prop 1 prop 2 0.3340081 0.3457627 Wish to test H : alcohol consumption and breast cancer are independent vs. H a : alcohol consumption and breast cancer are not independent.consumption and breast cancer are not independent....
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solutionset11 - Problem Set 11 Solutions STAT 3022 section...

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