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The passage around this formula

​ . To bound that uncertainty to a half-width e at a chosen confidence level z , the standard requirement is $n \;\geq\; \frac{z^{2}\, p(1-p)}{e^{2}}$. which, for a rate near one half and a 95% confidence interval within five percentage points, already calls for several hundred independent trials rather than five or ten. The practical conclusion is not that every team needs a statistics department before shipping a tool; it is that “it passed when I tried it a few times” and “it passes at a known, bounded rate” are different claims, and only a CI-integrated harness run at real scale can make the second one.

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