Public Knowledge Library / Critical Thinking

08 4 min read

Correlation isn't causation

Two things changing together might mean one caused the other, but it might also mean the arrow runs backward, a third factor is involved, or the pattern is just noise.

Four possibilities

A causes B

This is the story people usually jump to first, but it is not the only explanation.

B causes A

Sometimes the direction of the relationship runs the opposite way from the one you assumed.

C causes both

A hidden third factor can make two things move together without either one causing the other.

Coincidence

With enough data and enough comparisons, unrelated patterns sometimes line up by chance.

The caution

Before you claim a cause, ask what else could explain the pattern.

That one habit protects you from a surprising amount of bad reasoning.

Why it matters

Good critical thinking slows down before it concludes.

Strong explanations do more than notice patterns. They test timing, alternative causes, and whether the data is broad enough to support the claim.

Three checks worth making

01

Look for a third factor

A lurking variable is often the cleanest explanation for a suspiciously neat pattern.

02

Check the timing

A cause must come before its effect. If the sequence is wrong, the claim is wrong.

03

Distrust tiny samples

Small or cherry-picked data can make random noise look meaningful.

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