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:

In Remission

Clinic A

Clinic B

Died

4

4

Survived

296

196

TOTAL

300

200

Active Cancer

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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