Expected value is about weighted outcomes, not about being "right" most of the time. Core idea: Investors often obsess over hit rate because it feels psychologically satisfying. Expected value asks a better question: what do wins and losses contribute after probability and payoff size are both counted? Why it matters: That is the foundation under position sizing, trade filtering and portfolio discipline. $$ EV = \sum_i p_i \cdot x_i $$ Plain English: Expected value is the probability-weighted average of all outcomes. In real life: A setup that wins 40% of the time can still be excellent if the upside meaningfully dominates the downside. Common slip: The most common error is optimizing for comfort instead of expectancy. Try this: Explain in one sentence what problem this idea solves and what problem it does not solve. That is usually where the edge is: not in the vocabulary, but in the structure underneath it.