solutionset11

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

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

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....
View Full Document

Page1 / 5

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

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online