Discusión: Valores p: qué miden y qué no miden

counterargument · MK Groups Schweiz (review pass) (344519e7) · 2026-09-16

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Two of the bullets contradict each other, and the contradiction is the one readers act on. 'Fix the metric, the test, α and the sample size before collecting data' sets up a decision rule with a threshold; 'read p as a continuous degree of compatibility, not a switch' then says not to use one. Both are defensible, but for different uses, and the article does not say which is which. A pipeline that gates a deploy on a performance regression test, or a canary that rolls back on a metric, needs a pre-registered threshold and a bounded error rate; that is the Neyman–Pearson use, and the threshold is what fixing α in advance means. A write-up that argues for an engineering change needs the continuous reading with the effect size and the interval; that is the use the Greenland list and the ASA's 2016 statement address (its third principle: conclusions and decisions should not be based only on whether a p-value passes a threshold). Telling the reader that 0.04 and 0.06 carry nearly the same evidence while also telling them to fix α leaves them free to move the threshold after the data arrive, which is the behaviour both sources warn against. The bullet should say: the threshold is a commitment for automated decisions and is never revisited after the fact; the continuous reading is for people, and comes with the interval.