What a 70% Chance Actually Means (Bar Math)

Every so often a regular leans over the bar and says, "So if you tell me this trade's got a 70% chance, that means it's gonna work, right?" And I have to do the thing every good bartender has to do eventually: gently tell them they're wrong, without making them feel dumb about it, and without letting them walk out still confused.

So let's do the bar math version. No spreadsheets, no Greek letters. Just marbles.

The jar of marbles

Imagine a jar with 100 marbles in it. 70 are green, 30 are red. You reach in, you don't look, you grab one. Green means the trade works out the way we expect. Red means it doesn't.

A "70% chance" call means we think this specific setup looks like a 70-green jar. It does not mean you're guaranteed a green marble. It means that if you did this exact draw 100 times — 100 similar setups, same shape, same conditions — roughly 70 of them should come up green and roughly 30 should come up red. Every single time you play, you might still get red. That's not the system failing. That's the jar working exactly as advertised.

Why "70%" and "certain" are not the same word

Here's where people get burned, and not just in trading — in weather forecasts, in medical odds, in everything. They hear "70%" and their brain quietly rounds it up to "yes." It isn't yes. It's "more likely than not, but a real chunk of the time it won't." Almost one in three draws from that jar comes up red. If you're not mentally prepared for that, a single red marble feels like betrayal instead of what it actually is: the expected minority outcome showing up on schedule.

This is the whole reason we don't say "signal" at Trading Tavern. A signal sounds like an order. A probability is an honest description of a jar. We'd rather you know exactly what jar you're reaching into.

How we know our jars are actually 70-green, and not lying to you

Anybody can slap a number on a trade idea. The number is worthless unless it's checked against reality afterward. That's what our Truth Meter is for — it tracks, in public, whether our "70% calls" actually land green about 70% of the time over the long run, not just this week when it's convenient for us. If our 70s were secretly behaving like 50s, you'd be able to see that. That's the deal.

What to actually do with a 70% call

Treat it as good odds, not a sure thing. Size it like good-but-not-guaranteed odds — which is exactly what our position sizing approach is built to do automatically. And when the red marble comes up (it will, roughly 3 times in 10), don't treat it as proof the system's broken. Treat it as the jar doing exactly what it said it would do.

Back to the blog for more of this, or go see the receipts for yourself on the Truth Meter.