The Null Hypothesis

In a court of law, the defendant is innocent until proven guilty. In science, the universe is boring until proven interesting.

This is the Null Hypothesis ($H_0$).

The Default Position

The Null Hypothesis states that there is no relationship between two variables.

• "Smoking does not cause cancer."
• "This pill does not lower blood pressure."
• "Telepathy is not real."

We assume this is true.

The Burden of Proof

The scientist's job is to find evidence so strong that the Null Hypothesis looks ridiculous.

We do not prove the alternative. We reject the null.

It is a double negative. We don't say "The drug works." We say "It is highly unlikely that the drug does not work."

Why It Matters

If we assumed everything was true until proven false, we would believe in ghosts, aliens, and magic beans.

The Null Hypothesis is our shield against nonsense. It forces us to be skeptical.

The Diagnosis

When you read a paper, remember: the starting point was "this is nothing." The paper is an argument against that.

If the p-value is high (> 0.05), the Null Hypothesis wins. The defendant walks free.