A pattern's match score is not a probability

Automated pattern detection usually reports a score — “88% head and shoulders”, “92% bull flag”. It is tempting to read that as “a 92% chance this plays out”. It isn’t, and the gap between those two meanings is worth being precise about, because the whole value of a match score depends on not misreading it.

Match percent measures geometry

A match score answers a shape question: how closely does this stretch of price fit the ideal geometry of the named pattern? A 92% flag is a very flag-shaped flag. That is genuinely useful — it filters the near-misses and tells you the software is confident about what it’s looking at. It says nothing about what price does next. A perfect-looking pattern and a coin flip about the outcome can coexist happily.

Reliability is a separate, historical thing

How often a well-formed pattern has been followed by the move it’s associated with is a different measurement entirely — a historical base rate, studied and tabulated by people like Thomas Bulkowski over large samples. A good tool shows the two numbers separately: the geometric match for this instance, and the historical reliability of the pattern in general. Keeping them apart is what stops a tidy shape from masquerading as a forecast.

Using both without fooling yourself

• Match score screens for quality of shape, so you’re not reacting to a pattern that’s barely there.
• Reliability sets expectations, and even a “high-reliability” pattern is a base rate over many cases, not a promise about your one.
• Neither is a prediction. A pattern is context — a reason to look closer, plan, and manage risk — not an instruction, and not a probability for your specific chart.

A match score is the software showing its work: here is how well this fits, and here is what the shape has tended to do historically. Read it as evidence to weigh, and it sharpens your judgement. Read it as a probability, and you’ve invented a certainty the number never claimed.

Analess is an analysis tool, not investment advice. Nothing here is a recommendation to buy, sell, or hold anything.