statistics-reference

# Statistics Reference for Product Managers

## p-value

The p-value is the probability of observing data at least as extreme as yours if there were no true effect.

- Small p-value means data is less consistent with "no effect".
- It does not tell you the probability that the variant is best.

## Confidence Interval (CI)

A CI gives a plausible range for the true effect size.

- Narrow interval: more precise estimate.
- Wide interval: uncertain estimate.
- If CI includes zero (or no-effect), di