Calculate and interpret measures of effect in different epidemiologic study designs.
A. A cohort study is conducted to assess the association between clinical characteristics and the risk of stroke. The study involves n=1250 participants who are free of stroke at the study start (baseline). The data in Table 4 below shows hypertensive status measured at baseline and incident stroke at five years.
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Table 4. Hypertension status at baseline and stroke five years later |
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Stroke at 5 years |
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Hypertension at baseline |
Yes (+) |
No (-) |
|
Yes (+) |
18 |
234 |
|
No (-) |
46 |
952 |
B. A case control study is conducted to assess the relationship between heavy alcohol use during the first trimester of pregnancy and miscarriage. Fifty women who suffered miscarriage are enrolled along with 50 who delivered full-term. Each participant’s use of alcohol during pregnancy is ascertained. Heavy drinking is defined as four or more drinks on one occasion. The data are shown in Table 5.
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Table 5. Alcohol use and outcome during pregnancy |
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Miscarriage |
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Heavy alcohol use |
Yes (+) |
No (-) |
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Yes (+) |
14 |
4 |
|
No (-) |
36 |
46 |

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