Why does peeking at an A/B test inflate false positives, and how do sequential and always-valid tests fix it?

Checking an experiment every day and stopping when it hits significance can triple your false-positive rate. The signal is knowing why, and the family of methods that make continuous monitoring valid. Here is the answer.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.