It depends what you mean by probability, but your smart guy, I know you don’t mean probabilities strictly in the sense of “odds”.....
Ummm he said: " .... assuming it is liquid enough and no overnight trading) ....." For someone who throws out nonsense strawman claims right and left .... and left and right I suggest you slow down with the insults and hysterics and read little more closely in the future.
I sense the OP is an west coast Asian American (Asian Canadian), not that is matters if I am right or not.
A stop loss works when it matters the least, and doesn’t work when it matters the most. He puts it as a defined risk and assumes only if it’s liquid enough. But when we bring this to the real world and begin to deploy a strategy, for sake of survival, we cannot assume liquidity will always be there. We need to take more measures and truly define our risk.
Probabilities (or risk) of an event happening. I never speak of risk and reward because first of all most get it backwards when they say my strat has r/r of 3 to 1 when of course they are not risking (at least they don't think so) 3 to win 1. They are risking 1 to get a reward of 3 - as the vast majority of the trading community put things i.e. risking rewarding. Secondly as the top line states risk is of an event happening, not the possible bad outcome resulting from an unexpected event takes place. Once in a trade trading funds can either increase or decrease, not be risked any more than the fact they are at play in a trading account.
You assume price movements are random without providing any proof. Most successful systems have between hundreds to thousands of data points that allow one to calculate a Sharpe ratio. Win rate percent is determined in forward tests with real money. For example, one of my systems that traded real money had a 64% win rate over time. That is not luck. That is Stats which I got an A in college. Price movements can be caused by anything like : https://www.marketwatch.com/story/s...a-trade-developments-2019-09-24?siteid=YAHOOB Once an event occurs it causes Price movement wave patterns which I will not explain here, but they can be traded successfully until the next event occurs.
This is an impossible debate to prove or disapprove. A trader with audited statements for many years (long term like > 10 years) is not going to waste time trying to prove that their profits are via technical analysis regardless if he/she used only 5% TA or 90% TA. Anything less than the above will be cleverly dismissed as luck. Thus, the only thing you can prove are that you're profitable, you use technical analysis but you can not eliminate other variables that a typical trader would be using with their technical analysis such as discipline, trade experience and anything else that may not be related to trading. In the old debate threads about TA, I've seen charts posted, broker statements posted, statistics posted, links to academic articles, links to books...then there are the clever ones that say give me access to what's working for you so that they can closely examine if it work or not work. The only thing that should matter is if you can get out of the market with your profits before the risk of ruin occurs. Actually, risk of ruin is not your only worries...other things can go wrong that's not related to your finances. P.S. Two ET members arguing about TA decided to meet in some nearby city to decide who is right via their fists...one guy showed up with his big friends and the other guy showed up with a knife. True Story ? wrbtrader