Randomized trials translate management hunches into falsifiable bets. R. A. Fisher’s The Design of Experiments (1935) supplied the mathematics; today, online platforms run thousands of A/B tests to estimate causal impact, as documented in Kohavi, Tang, Xu, and Chen’s Trustworthy Online Controlled Experiments (2020). A product team that suspects a new checkout design will lift conversions can specify a hypothesis, exposure rules, and success metrics before launch. Rather than “liking” a design, they quantify uplift and guard against novelty effects. Yet numbers, by themselves, can seduce, which is why Deming placed variation at the center of managerial thought. [...]