this is a very big topic..
- first of all most people have the wrong approach to the market - it's understandable as when he begins he doesn't understand what the market is, so he looks at it as some sort of mysterious monster, and therefore he goes to the book store to read 'technical analysis 101', which takes the same perspective - a mysterious monster that emits mysterious signals that somehow can be captured by math formulas with no rhyme or reason.. then he hears about back testing and system trading, a very attractive idea - find some magic, let the machine make money while he lies on the beach.
- so this thread already discussed the problems with this approach - the self-defeating fate of any of these methods based on mystery discovered by back test.... inevitably any profitable pattern is discovered by thousands of people... they get crowded and become vulnerable to counter strikes (aka fails).. so the trader just keep going yo-yo between profits and losses, going nowhere.
- the other big problem with back test is it completely ignores the context, the back drop, the story of the day/week/month/year.... as if price moves simply because random people having random thoughts in an isolated environment, which can't be further from reality..... some day, when AI is advanced enough, and can back test price movement with every news release every viral social media piece etc, then we are talking about the discovery of the true human behavior in the market.... armed with that tool, you can go forward and trade it... because human mature does not change and your system won't self defeat.... but you can imagine the resource required to develop such a system... probably only available to some party like Google Deepmind, which currently is just too busy solving other problems... if they devote to the financial markets they will kill everybody else.... currently these HFs label themselves as AI.... they are really not... systems are terrible, can't even beat the index.
- which goes back to what I always advocate - you have to take the stories into consideration... examples in my 'trading is easy' thread.... there is no need for back test... impossible to do anyway due to the reasons above... you just need to get on the same page with the pro boys, which essential boils down to a few tricks - when the dumb money is long, knock them dead with price action and media manipulation; when the dumb money is flat/short, pull it up until they are long again.... you can observe this over and over with earning cycles and news cycles - the past few in recent memory being: China slow down, oil crash, inflation scare, fiscal cliff, yield curve inversion aka fake recession scare.... please do yourself a favor, review the play by play of these cycles from mid 2015, you will see how the pro boys play this game and hopefully you can get on the same side, and when you do this exercise, do this slowly, daily price bars, and very importantly, the daily news releases.....
- which leads to my final point, after doing the work above, most people probably still won't get it... it does require some analytical thinking skills and a minimum IQ of 120, preferably 140 (if you have 140 this stuff will come quite easy for you).... but the big silver lining is, dollar cost averaging on the QQQ doesn't require any skill, other than a firm belief that investing in America and technology of tomorrow will make you rich so you can stick to it thru the thick and thin.