Data Verification

Your arithmetic is probably fine. That is not where analyses go wrong.

How to use this

Trigger: you are about to state a number, a comparison, or a causal claim that came out of data and that someone will act on. "The strategy makes money." "Churn is worse on the enterprise tier." "Fees are what killed it." "Cohort B converts better."

Cost: questions 1 and 2 are the routine minimum and usually take a few minutes. They target the failure modes behind ~79% of the audited corpus below, which is a statement about where those errors came from, not a measured catch rate against them. Do not skip them because the analysis felt simple; every incident in that corpus felt simple.