Probability vs Prediction: What Traders Get Wrong About Uncertainty

Many traders believe good trading means predicting correctly. If the next move can be known, the rest seems simple. The problem is that the next move cannot be known with certainty.

A good trade can lose

Chapter 11 makes a distinction that changes how a trader interprets results: the quality of a decision and the quality of its outcome are not the same thing.

A trade can follow the plan and still lose. Another can break the plan and still make money. If you judge the decision only by the result, you can learn exactly the wrong lesson.

Think in distributions, not certainties

Probabilistic thinking does not mean becoming vague. It means changing the language of the decision. Instead of “this will go up,” the trader can think, “across similar setups, this process has produced positive results, but this trade can still lose.”

That shift matters because it makes uncertainty part of the plan rather than a surprise.

Expectancy is the bridge

The book introduces expectancy as a simple way to combine win rate, average win, average loss and costs. A strategy can win less often and still have positive expectancy if its winners are sufficiently larger than its losers.

This is one reason win rate alone can mislead. Being right often is not the same as having a favorable average result.

The book also cautions that expectancy is an estimate based on a sample. A positive expectancy does not remove losing streaks, protect against oversizing, or predict the path of the next hundred trades.

The better question

You do not need to know what will happen next. You need to know what you will do, whichever way it goes.

That is the practical value of probabilistic thinking. It moves conviction away from the outcome and toward the process.

The goal is not to trade without conviction. It is to be confident in a process while remaining genuinely uncertain about the individual trade.