Every real analysis runs into the same quiet decision, over and over: where do you draw the line? How many reviews before a rating is trustworthy? How many purchases before a customer counts as "active"? How many chart appearances before an artist counts as "known"? These cutoffs shape every result downstream — and the difference between an amateur and a professional is not which number they pick. It's whether they can defend it. This guide covers the method, the classic statistical trap that makes floors mandatory, and worked examples from open projects.
The two ways to pick a number
Method one: it feels right. "Let's say 100 reviews minimum." Round number, sounds reasonable, took four seconds. Method two: ask the data. Measure how the values actually distribute, count what each candidate cutoff keeps and discards, then choose the one whose meaning, said out loud, matches what you're trying to capture. Method one survives until the first person asks "why 100?" Method two is the answer to that question.
The test of a good threshold: you can say it out loud with a reason attached, and the reason references the data. "5+ charted songs, because the measured distribution shows 57% of artists chart exactly once — 5+ means the industry demonstrably came back to this artist across a career." Not "5 felt right."
