<b>Roughly 6-8% of running A/B tests carry a Sample Ratio Mismatch — and most teams never check.</b>

<b>Roughly 6-8% of running A/B tests carry a Sample Ratio Mismatch — and most teams never check.</b>
You split 50/50 but observe 50.8/49.2 on 80k users. Feels like noise. Run a chi-square test: a 0.8pp skew at that volume is wildly unlikely by chance, meaning your randomizer, redirect, or bot filtering is broken.
— Any SRM (the assignment ratio doesn't match what you set) invalidates the whole result, win or loss.
— Check it <i>before</i> you read the conversion number, not after.
Read the number, not the story. [SRM threshold p&lt;0.001]