I just wanted to add... somebody mentioned earlier that Mark was a 'failed trader'... in his course 'How to think like a professional trader' he shares some of his background explaining how he was initially relying on brokers to make the decisions for him, and the first tipping point was when he was losing lots of money, couldn't take it anymore so asked the broker to get him out of the trade. Practically soon after exiting, the market started going in what would have been his favour and he recounts how he would have sat on a 400k trade on just 2 contracts. So he decided he had to figure out how to trade by himself and moved to Chicago.

Eventually he lost all of his money trading and had to declare bankrupcy but it was at that point something clicked in his mind - it was probably the ligthness of having nothing more to lose that made him change attitude - that's when he 'got it', which I assume means he started being consistently profitable.

Which brings me to a question, although I just realized I'm a bit off-topic so I'll post it in another thread

Edit: I was going to ask the question 'is blowing up an account x times a necessary part of the experience and path to consisten profitability?' but I have seen that it is sort of addressed in this thread so I'll carefully read that and make my own conclusions...

I listened to the interview of Mark.

I think the quote that Ron highlighted was:
"The outcome of anyone particular trade is a completely random event."


Mark later talks about recommending traders trade in "samples" e.g 20 trades groups.
He does admit that there is a statistical edge (if the trader has defined an edge) to the outcome of a series of trades
(let's say 60%) and then goes on to talk about roulette tables, con flips, and slot machines.

While I believe I understand what Mark is getting at I think it is more correctly stated.
"The outcome of any one particular trade is not completely known."

I think the quote that Ron highlighted was:
"The outcome of anyone particular trade is a completely random event."

While I believe I understand what Mark is getting at I think it is more correctly stated.
"The outcome of any one particular trade is not completely known."

Agreed. Long ago, I promised myself that I would never, ever weigh in on the phrasing that "the probability of the next trade is 50/50," since the issue is purely semantic, and everyone is always talking past each other when they disagree on it.

But I am weak.

Here's why I am saying it is semantic:

The next trade's outcome is unknown, and can't be known. You just have to shrug and take the trade that you are supposed to, knowing that you won't know the outcome until it's done. Many people will say, that means it's a coin-flip, or it's 50-50, or it's random, or it's a toss-up, or it's a matter of chance, or I don't know, or it's up to the trading gods, or who knows what will happen. All those statements mean the same thing to the people who make them: you don't know what will happen with this individual trade. From a practical standpoint, you should just trade according to an edge that you have tested over time, knowing that you are in it for the long run, not the individual trade. The individual trade outcome can never be known ahead of time. So don't sweat individual trades, just trade your edge consistently.

That's what is meant, and I have no problem with it, and I should stop typing now .... But here we go

If you say that something is 50-50, or has a 50% probability, or has even odds, you're not really saying that the outcome is not known (although that may be what you mean.) You are saying that if you do it a large number of times, about half the time it will come out one way and half the other. That is a very definite statement, not a statement about unknowns, and it matters. If you are betting on a game, and you have even odds, you should not expect to win much. If you think the probabilities are in your favor, that's not 50%, it's whatever probability it is -- but the outcome of the next event is still not known, only the likely outcome of a large group of similar events.

Say you are playing a coin-flip game where you are betting on heads or tails with a fairly-weighted coin. After a hundred flips, you won't have won much, if any, money. It would have been heads about 50 times, tails about 50 times -- maybe 49 to 51 or something, but very close to 50 of each. Now suppose you are cheating, and you use an unfairly-weighted coin that comes up heads 60% of the time. You still don't have any way to know what the outcome of any one flip will be, but you should bet consistently on heads, and you will do well over time. (And also probably have to leave the game early, and in a hurry.)

Confusion comes in because probabilities apply only to groups of events, not to just one by itself. We do want to apply what we know about the odds of a situation to a particular event. We can only do that if we understand that we really are talking about what is likely to happen if the event is repeated many times, but not actually what this one event "will" do, which the probabilities simply do not address. But "unknown" is not "50-50", it's unknown. 50-50 is an actual, definite number: it means that, in the long run, a particular outcome will happen about 50 times out of a hundred, not that this trade's outcome cannot be known in advance, which it can't, and is unknowable in advance, which it is.

OK, got that off my chest. I do agree with @aquarian1 about what the actual best meaning of the statement is.

I admit that this is semantic, and also nit-picking, so I will stop now.

Bob.