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Glossary
False Negative (Type II Error)
Failing to detect a real difference between variants.
What is a False Negative?
A false negative (Type II error) occurs when there is a real, positive difference between your variants, but your test fails to detect it.
Why They Happen
The most common cause of a false negative is a **small sample size**. If you don't have enough traffic, the real improvement might be hidden by random noise.
The Cost of False Negatives
A false negative is a missed opportunity. You might discard a great idea simply because you didn't run the test long enough to prove it works.