Twyman's law states that "Any figure that looks interesting or different is usually wrong", following the principle that "the more unusual or interesting the data, the more likely they are to have been the result of an error of one kind or another".

Twyman's law - Wikipedia

データ分析をしていて面白いことに気づいたときにまずすることはデバッグであり、A/B テストのインフラは "guardrail metric" を用意しような、という文脈で出てきた格言。