SIMPSON’S PARADOX

How does it happen?

?

?

?

Pamela Leutwyler

A perfume company is testing two new scents:

Citrus

And

Orange blossom

28 single women volunteer to test these products

15 are Eagles cheerleaders

13 are members ofGranny’s bingo club

13 women choose CITRUS

15 women choose ORANGE

4 OF THE 5 CHEERLEADERSWHO USED CITRUS FOUND LOVE!

80% success rate

7 OF THE 10 CHEERLEADERSWHO USED ORANGE FOUND LOVE!

70% success rate

CITRUS appears to be more effective for cheerleaders

80% success rate70% success rate

2 OF THE 8 GRANNIESWHO USED CITRUS FOUND LOVE!

1 OF THE 5 GRANNIESWHO USED ORANGE FOUND LOVE!

CITRUS appears to be more effective for grannies

25% success rate 20% success rate

80% success rate70% success rate

25% success rate 20% success rate

CITRUS is better for cheerleaders

CITRUS is better for grannies

6 of the 13 women who usedCitrus found love. 46%

8 of the 15 women who usedOrange found love. 53%

Overall Orange has a higher success rate

How can it happen thatCITRUS works better for cheerleaders and

CITRUS works better for granniesWhile

ORANGE works better overall???

Where are most of the grannies?

Where are most of the cheerleaders?