Table 1 |
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|
Individual vs. ecologic data |
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| Individual (interior cells) |
Ecologic (margins) |
|||||
|
|
|
|||||
| exposed |
unexposed |
sum |
exposed |
unexposed |
sum |
|
|
|
||||||
| cases |
16 |
12 |
28 |
? |
? |
28 |
| noncases |
24 |
48 |
72 |
? |
? |
72 |
| total |
40 |
60 |
100 |
40 |
60 |
100 |
| risks |
0.4 |
0.2 |
X |
0.40 |
||
| RD |
0.2 |
Y |
0.28 |
|||
| n |
100 |
|||||
|
|
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|
Individual-level information on exposure and outcome are shown by the interior of a two-by-two table; they are summarized by the risks in the unexposed and exposed and the risk difference (RD). Ecologic studies possess only the margins of the table, summarized by the average exposure X, average risk Y and group size n. |
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|
Webster Environmental Health 2007 6:17 doi:10.1186/1476-069X-6-17 |
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