Rtharp:
I read both books written by your father and they are the best ones I have ever read about trading.
I also use a sector daytrading approach on NYSE stocks, trading only 100 shares with Interactivebroker's 0.01$ commissions. I have been trading this system with real money for 3 months and since I started trading it, it has been slightly positive. But I consider 3 months to be too little time to verify a robust system. I really dont know if this style of trading is negative expectancy in the long term or not, because it is so subjective and discretionary that it cannot be backtested. So as far as position sizing is related, I am practicing with the smallest share size I can get on the NYSE without going into odd lots. I must admit that I can be profitable trading with as little as 100 shares because my commissions is low compared to other brokers, so 0.02$ of profit on 100 shares and I am immediately breakeven.
As I said before, I am a big fan of your father's books. I will really appreciate if he writes a book on trading systems design (go tell him) And his books took me several readings to understand (traits of a good book). But what I don't understand about the markets it that you CAN'T readily calculate probabilities as in a casino game. Market/stock/futures variables are too complex and there is no rule that says you can win 70% of the time in any market. In contrast, casino games such as roulette, craps, blackjack, video poker, you can readily know your probabilities with some number crunching and immediately adjust your position size accordingly (of course most of those games are negative expectancy games in the long term). You can even derivate some optimal playing strategies for these games, since it is a "closed" game.
By closed game I mean a game that you can calculate its probabilities and expectancies and be sure it will continue that way as long as it is not rigged.
That is why some people say backtesting is useless and only represents past historical testings that may or may not continue.
You mentioned about your positive expectancy system. Is it complex ? ? Have you backtested it ? Did you develop it or you borrowed it from someone else. My sector daytrading approach was borrowed and I modified it a bit to fit me, but I am still unsure if it is a positive expectancy system because I have no way to backtest it.
Another problem I may have is that since I trade at home alone, I dont have other traders to share ideas with.
hsanson