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Did you know that when ice cream sales rise, so do property crime rates?

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What do you think causes the two events to occur together?

3
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The explanation is that property crime peaks in the summer because of warmer weather, more people on vacations (leaving their homes vacant), teenagers out of school, and so on.

4
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It just happens that ice cream sales also peak in those months because of the weather.

5
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It is a case of a third variable causing both to occur.

6
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Or what if there were a positive correlation between sales of cigarette lighters and the incidence of cancer?

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The suspect might well turn out to be the omitted variable (the so–called “smoking gun”): the cigarette.

8
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Or what if research revealed that parents who bought parenting books were “better” parents?

9
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Does that prove the books work?

10
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Or is it possible that people who would buy books on parenting tend to be “better” parents?

11
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That is, it might be about the parents, not the book.

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Causality is tricky stuff.

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Be careful.