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I don't get that. It would be true if he just made a few trades, but the author claimed to be making 2000 trades a day. Over a period of months winning that wouldn't qualify as blind luck.



Definitely not blind luck; but boosted by the fact that SPY was on a massive bull run at that time.

This is really cool, any way you cut it.


>Over a period of months winning that wouldn't qualify as blind luck.

Why not?


It's simple statistics. The author was up 4k/day over 120 days. He doesn't say what his daily volatility was, but let's assume 2k (which squares pretty well with his claim that his worst day was a 2k loss).

With a quick bit of R code, we can simulate his PnL over 120 days multiple times, assuming he has no skill, and see what the probability of him being up 4k/day is. I'll use a t-distribution with 3 degrees of freedom, which allows big up and down swings (again, accentuating the effect of luck).

    > pnl <- c()
    > for (i in 1:1000) pnl[i] <- mean(2000 * rt(120, df=3))
    > mean(pnl > 4000)
    0.0
That is, there's a zero percent chance that he would have made those returns if he had no skill. And remember that this simulation is overestimating the effect of luck.


By that definition you could start claiming everything as blind luck. Why bother doing anything at all, let luck do the work.




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