Imagine you’re a detective checking an alibi. Your starting position is: “This person is innocent unless the evidence clearly shows otherwise.” That default assumption is like the null hypothesis.

In statistics, the null hypothesis is a formal way of saying, “There is no real effect, no real difference, nothing special happening.” For example, “This new drug works the same as the old one,” or “This ad does not change sales.”

We then collect data and test whether the evidence is strong enough to reject that starting assumption. If the evidence is strong, we reject the null hypothesis and say something likely is going on.

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