Sanderson M. Smith
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EXAMPLE OF SIMPSON'S PARADOX (MINI-PROJECT BY EMILY)
Emily's project illustrates Simpson's Paradox, which refers to the reversal of the direction of a comparison or an association when data from several groups are combined into a single group.
Emily's data, which might not show up well in the picture, compares two clinics. The chart on the right in the picture has this data.
|
Clinic A |
Clinic B |
Died |
26 |
8 |
Survived |
874 |
292 |
TOTAL |
900 |
300 |
Clinic A lost 2.89% of its patients and Clinic B lost 2.67% of its patients.
But... here are the figures that make up the total shown above:
|
Clinic A |
Clinic B |
Died |
4 |
4 |
Survived |
296 |
196 |
TOTAL |
300 |
200 |
|
Clinic A |
Clinic B |
Died |
22 |
4 |
Survived |
578 |
96 |
TOTAL |
600 |
100 |
In the two categories that make up the total, Clinic B loses a greater percentage of its patients than does Clinic A. Check it out!
Simpson's Paradox in action.
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