Is a higher expectancy always better?
Not necessarily. A strategy with $50 expectancy per trade taken 5 times a month might be less reliable than one with $20 expectancy taken 50 times. Also, expectancy calculated from a small sample (10–20 trades) is noisy; a lucky streak can inflate it. A modest, consistent positive expectancy across hundreds of trades is more trustworthy than a large expectancy from a few trades.
How is expectancy different from average profit per trade?
Expectancy is weighted by win/loss rates and sizes; average profit per trade is simply total profit divided by number of trades. If you have 10 wins of $100 and 90 losses of $10, your average profit is ($1,000 − $900) ÷ 100 = $1 per trade. But your expectancy is (0.10 × $100) − (0.90 × $10) = $10 − $9 = $1, which happens to be the same in this case. The formulas can give different insights depending on how you group and weight outcomes.
Can I calculate expectancy from my Mantis journal?
Yes. Export or review your trade history in Mantis, then tally your win count, loss count, average win size, and average loss size. Mantis stores all data locally on your device, so you have full access to your trade records. Plug those numbers into the expectancy formula. Many traders also use Mantis to track win rate and average risk per trade, which makes expectancy easier to compute.
What if my expectancy is positive in backtests but negative in live trading?
This is common. Reasons include: slippage and commissions eating into thin edges, psychological pressure causing you to exit winners early or hold losers too long, market conditions changing so the past pattern no longer works, or overfitting your rules to historical data. Expectancy is only valid if your live trading behavior matches your backtest assumptions.
Does positive expectancy guarantee I'll make money?
No. Expectancy is a long-term average; short-term variance is real. Even with +$20 expectancy per trade, you can have a 10-trade losing streak and lose money. You also need sufficient capital to survive drawdowns, correct position sizing, discipline to follow your plan, and enough trades for the law of large numbers to work. Positive expectancy is necessary but not sufficient.
