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I'm saying it's not reasonable to think that a private individual can make a long-term profit day-trading, skilled or not. It's quite reasonable to suppose lot

• dietrichepp 10y ago
  There are professional day traders who earn an income over the long run by day trading. This is a true fact. It seems like you are trying to contradict this fact… or do I misunderstand what you are saying? The model I gave was the simplest model I could think of that would let you test the theory that skill is a factor in day trading. It was an illustration of how someone with mathematical training might think about statistics like "80% of day traders lose money" without jumping to the false conclusion that all traders eventually lose money.
  • thedevil 10y ago
    > There are professional day traders who earn an income over the long run by day trading. This is a true fact. Got anything to back up this "fact"? > The model I gave was the simplest model I could think of that would let you test the theory that skill is a factor in day trading. You can't assume the existence of skill proves the existence of long-term profits. Nor can you even assume that a good up/down ratio proves skill without considering the magnitude of the ups and downs or the impact of compounding.