Expectancy is the average outcome per trade, calculated as win rate multiplied by average win minus loss rate multiplied by average loss. It is the only headline metric that resolves the tension between hit rate and payoff: a seventy percent win rate is unprofitable if losses are three times the size of wins, while a thirty-five percent win rate can be strongly profitable with a three-to-one payoff.
For gold specifically, expectancy must be calculated net of spread, swap and commission, because on XAUUSD those costs consume a meaningful share of a small target and frequently turn a positive gross figure negative. It should also be segmented by session, setup and volatility regime, since a blended positive number can conceal a persistently negative cohort that keeps a trader in the losing half of their own system.