Quiz 8, Module Case-control
8. How would you set up the classic 2x2 table using the above information to test the hypothesis that cases are more likely to have ingested EnduroBrick than controls?
- See the 2x2 table
- Calculate the odds of exposure among cases
- Calculate the odds of exposure among controls
- Calculate the exposure Odds Ratio (OR)
- Calculate the odds of Susser Syndrome among the exposed
- Calculate the odds of Susser Syndrome among the unexposed
- Calculate the disease Odds Ratio
- Interpret your findings
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|   | Case | Control | Total |
|---|---|---|---|
| Exposed (Endurobrick) | 28 | 56 | 84 |
| Unexposed (No Endurobrick) | 84 | 168 | 252 |
| Total | 112 | 224 | 336 |
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Odds of exposure among cases (# of Cases exposed) / (# of Cases unexposed)
28 / 84 = 0.333
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Odds of exposure among controls (# of Controls exposed) / (# of Controls unexposed)
56 / 168 = 0.333
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OR = (Odds of Exposure among Cases) / (Odds of Exposure among Controls)
(28/84) / (56/168) = 1.0 or 0.33 / 0.33 = 1.0
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Odds of disease among exposed (# of Cases Exposed) / (# of Controls Exposed)
28 / 56 = 0.50
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Odds of disease among unexposed (# of Cases Unexposed) / (# of Controls Unexposed)
84 / 168 = 0.50
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OR = Odds of disease among Exposed / Odds of disease among Unexposed
(28/56) / (84/168) = 1.0 or 0.50 / 0.50 = 1.0
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Individuals with Susser Syndrome (cases) have the same odds of having ingested EnduroBrick as those without Susser Syndrome (controls). Conversely, individuals who ate EnduroBrick have the same odds of developing Susser Syndrome as those who did not eat EnduroBrick. An Odds Ratio = 1.0 suggests that there is no association between Susser Syndrome and EnduroBrick ingestion.
