The data are from Lesson 5 and are based on a 5 year cohort study of men initially diagnosed with CHD who were cigarette smokers. The exposure variable identifies whether the study subjects continued smoking (+) or quit smoking (-) after the CHD event. The outcome is whether they died (+) or were still alive (-) after five years of follow-up. The data are shown in the table below.
The results of the analyses are below:
2 x 2 Table Statistics |
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Single Table Analysis |
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Exposure |
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(+) |
(-) |
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(+) |
27 |
14 |
41 |
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Disease |
(-) |
48 |
67 |
115 |
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75 |
81 |
156 |
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Chi Square and Exact Measures of Association |
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Test |
Value |
p-value(1-tail) |
p-value(2-tail) |
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Uncorrected chi square |
7.041 |
0.003984 |
0.007968 |
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Yates corrected chi square |
6.108 |
0.006729 |
0.01346 |
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Mantel-Haenszel chi square |
6.996 |
0.004086 |
0.008171 |
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Fisher exact |
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0.006561 |
0.01312 |
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Mid-P exact |
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0.004369 |
0.008738 |
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All expected values (row total*column total/grand total) are >=5 |
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OK to use chi square. |
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Risk-Based* Estimates and 95% Confidence Intervals |
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(Not valid for Case-Control studies) |
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Point Estimates |
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Confidence Limits |
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Type |
Value |
Lower, Upper |
Type |
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Risk in Exposed |
36% |
26.04, 47.32 |
Taylor series |
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Risk in Unexposed |
17.28% |
10.46, 27.07 |
Taylor series |
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Overall Risk |
26.28% |
19.98, 33.72 |
Taylor series |
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Risk Ratio |
2.083 |
1.185, 3.661¹ |
Taylor series |
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Risk Difference |
18.72% |
5.086, 32.35° |
Taylor series |
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Etiologic fraction in pop.(EFp) |
34.24% |
9.541, 58.93 |
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Etiologic fraction in exposed(EFe) |
51.99% |
15.62, 72.68 |
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Odds-Based Estimates and Confidence Limits |
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Point Estimates |
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Confidence Limits |
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Type |
Value |
Lower, Upper |
Type |
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CMLE Odds Ratio* |
2.675 |
1.277, 5.763¹ |
Mid-P Exact |
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1.208, 6.142¹ |
Fisher Exact |
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Odds Ratio |
2.692 |
1.279, 5.666¹ |
Taylor series |
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Etiologic fraction in pop.(EFp|OR) |
41.39% |
14.88, 67.9 |
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Etiologic fraction in exposed(EFe|OR) |
62.85% |
21.81, 82.35 |
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*Conditional maximum likelihood estimate of Odds Ratio |
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(P)indicates a one-tail P-value for Protective or negative association; otherwise one-tailed exact P-values are for a positive association. |
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° ¹ 95% confidence limits testing exclusion of 0 or 1, as indicated |
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LookFirst items: Editor's choice of items to examine first. |
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