Is it possible to know the probability that a trade is successful?
If you had a trading system, and by trading system I mean the criteria setup that you will take a trade on, then once a setup comes up at what price will you open the trade and at what price you will close the trade. As an example, if you want to buy once price breaks through resistance at $10.00 you might place your buy order at $10.05. So once you have a written trading system you could do backtesting on this system to get a percentage of win trades to loosing trades, your average win size to average lose size, then from this you could work out your expectancy for each trade that you follow your trading system on. No. Like Keshlam said, unless you have a crystal ball there is no sure thing. However based on the things you said in your question, you could be better off doing some back testing. With your findings, you can then set up trades in your favor but again it's not 100%. You may also want to check out quant finance stackexhange.
Based on my research while asking How are unmarketable market orders (other side of the order book is empty) matched with incoming orders? and the one answer there, it seems like there are a few things for certain: All of this of course depends on the exact algorithm specified by the given exchange - I don't think there's a standard here. The problem is that while there are a lot of statistics that can be created from basic market data such as prices and volume, along with the fundamentals of the company, I think that if you talk to 8 different day traders, you'll get 12 different theories of how to interpret and trade based on those numbers.  Also quite likely, the more successful someone is at day trading, the more closely they are likely to guard their secrets and not want to divulge them. If there was any uniform concensus, they you'd see all the daytraders doing the same thing, and moving as a group, shortly after which you'd get 'contra' folks who would try to gain by moving in opposition, or 'predicta' folks who would try to front-run the pack. and.... (I think you can see where this leads)  A better idea might be to just work on educating your-self firstly with regard to nomenclature and terms, and then move on to reading some stuff about how markets work   etc.  I'd suggest starting with a book like 'Wall Street Words' and/or 'A Random Walk Down Wall Street' since both are great introductions to things, and move on from there.  Note that both of those books have gone through multiple editions, so be sure to get the most recent one (especially if you are trying to save money and buy a used version)   You are also likely to find an nearly endless supply of 'seminars' that will offer to teach you somebody's proven method for a fee, or for 'free' but after which you find our you need to use their special tools or data sources etc (which cost money) to use their 'system'  (either of which makes me think that their system can't be that great if they figure it's a surer thing to charge for 'teaching' or 'tools/services' than it is to use their system, otherwise they'd just shut up, practice what they preach and make money that way instead)  It might be worth attending the free ones just to get exposure to someone's theory on how to game the system, provided you are 'not an easy mark' and can withstand the high pressure sales pitch for their books/software/services etc that pays their bills and almost invariably comes along with such a seminar. I would argue for another type of lottery not mentioned that still denies trades but makes it impossible for a trade to improve on satisfaction. Basically shift from school level lotteries to student level lotteries. You use a lottery to rank all students, such that the students are ranked 1 through N. Where N is the total number of students. Student number 1 gets their top choice school. Student X gets their top school that's not already filled up. This student level, instead of school level, lottery then guarantees that it's impossible for a pair of students to trade and both get a better choice than what they got from the lottery. Given that hedge funds and trading firms employ scores of highly   intelligent analysts, programmers, and managers to game the market,   what shot does the average person have at successful investing in the   stock market? Good question and the existing answers provide valuable insight.  I will add one major ingredient to successful investing: emotion.  The analysts and experts that Goldman Sachs, Morgan Stanley or the best hedge funds employ may have some of the most advanced analytical skills in the world, but knowing and doing still greatly differ.  Consider how many of these same companies and funds thought real estate was a great buy before the housing bubble.  Why?  FOMO (fear of missing out; what some people call greed). One of my friends purchased Macy's and Las Vegas Sands in 2009 at around $5 for M and $2 for LVS.  He never graduated high school, so we might (foolishly) refer to him as below average because he's not as educated as those individuals at Goldman Sachs, Morgan Stanley, etc.  Today M sits around $40 a share and LVS at around $70. Those returns in five years. The difference?  Emotion.  He holds little attachment to money (lives on very little) and thus had the freedom to take a chance, which to him didn't feel like a chance.  In a nutshell, his emotions were in the right place and he studied a little bit about investing (read two article) and took action.  Most of the people who I know, which easily had quintuple his wealth and made significantly more than he did, didn't take a chance (even on an index fund) because of their fear of loss. I mean everyone knows to buy low, right?  But how many actually do?  So knowing what to do is great; just be sure you have the courage to act on what you know. The Sharpe ratio is, perhaps, the method you are looking for.  That said, not really sure beta is a meaningful metric, as there are plenty of safe bets to be made on volatile stocks (and, conversely, unsafe bets to be made on non-volatile ones). "You might consider learning how the ""matching"" or ""pairing"" system in the market operates.  The actual exchange only happens when both a buyer and a seller overlap their respect quotes.   Sometimes orders ""go to market"" for a particular volume.  Eg get me 10,000 Microsoft shares now.  which means that the price starts at the current lowest seller, and works up the price list until the volume is met.  Like all market it trades, it has it's advantages, and it's dangers.  If you are confident Microsoft is going to bull, you want those shares now, confident you'll recoup the cost.  Where if you put in a priced order, you might get only none or some shares. Same as when you sell.  If you see the price (which is the price of the last completed ""successful"" trade.  and think ""I'm going to sell 1000 shares"". then you give the order to the market (or broker), and then the same as what happened as before.  the highest bidder gets as much as they asked for, if there's still shares left over, they go to the next bidder, and so on down the price... and the last completed ""successful"" trade is when your last sale is made at the lowest price of your batch. If you're selling, and selling 100,000 shares. And the highest bidder wants 1,000,000 shares you'll only see the price drop to that guys bid.  Why will it drop (off the quoted price?).  Because the quoted price is the LAST sale, clearly if there's someone still with an open bid on the market...then either he wants more shares than were available (the price stays same), or his bid wasn't as high as the last bid (so when you sale goes through, it will be at the price he's offering).   Which is why being able to see the price queues is important on large traders. It is also why it can be important put stops and limits on your trades, een through you can still get gapped if you're unlucky.  However putting prices (""Open Orders"" vs ""(at)Market Orders"") can mean that you're sitting there waiting for a bounce/spike while the action is all going on without you). safer but not as much gain (maybe ;) ) that's the excitement of the market, for every option there's advantages...and risks... (eg missing out) There are also issues with stock movement, shadowing, and stop hunting, which can influence the price. But the stuff in the long paragraphs is the technical reasons." To complement farnsy's answer, I want to warn people against market prediction scams. If they give uniformly distributed buy/sell predictions to 256 people, one of them will get eight correct predictions in a row. They are trading a few cents of Amazon server time for 3% of your capital. "There seems to be a common sentiment that no investor can consistently beat the market on returns. What evidence exists for or against this? First off, even if the markets were entirely random there would be individual investors that would consistently beat the market throughout their lifetime entirely by luck.  There are just so many people this is a statistical certainty.  So let's talk about evidence of beating the market due to persistent skill. I should hedge by saying there isn't a lot of good data here as most understandably most individual investors don't give out their investment information but there are some ok datasets.  There is weak evidence, for instance, that the best individual investors keep outperforming and interestingly that the trading of individual investors can predict future market movements.  Though the evidence is more clear that individual investors make a lot of mistakes and that these winning portfolios are not from commonly available strategies and involve portfolios that are much riskier than most  would recommend. Is there really no investment strategy that would make it likely for this investor to consistently outperform her benchmark? There are so, many, papers (many reasonable even) out there about how to outperform benchmarks (especially risk-adjusted basis).  Not too mention some advisers with great track records and a sea of questionable websites.  You can even copy most of what Buffet does if you want. Remember though that the average investor by definition makes the average ""market"" return and then pays fees on top of that.  If there is a strategy out there that is obviously better than the market and a bunch of people start doing it, it quickly becomes expensive to do and becomes part the market.  If there was a proven, easy to implement way to beat the market everyone would do it and it would be the market. So why is it that on this site or elsewhere, whenever an active trading strategy is discussed that potentially beats the market, there is always a claim that it probably won't work? To start with there are a large number of clearly bad ideas posed here and elsewhere.  Sometimes though the ideas might be good and may even have a good chance to beat the market.  Like so many of the portfolios that beat the market though and they add a lot of uncertainty and in particular, for this personal finance site, risk that the person will not be able to live comfortably in retirement. There is so much uncertainty in the market and that is why there will always be people that consistently outperform the market but at the same time why there will be few, if any, strategies that will outperform consistently with any certainty." 90% fail 10% success  Just plug in some odds, because most of this is made up and a bunch of bologna anyway. Put a field in for their hurdle rate in the Excel spreadsheet and have your model always project 5% above their hurdle rate. "There is no simple answer to that, because no one knows exactly what the probability distribution of S&P 500 returns is. Here is a sketch of one possible way to proceed. Don't forget step 4!  The problem is that the stock market is full of surprises, so this kind of ""backtesting"" can only reliably tell you about what already happened, not what will happen in the future.  People argue about how much you can learn from this kind of analysis.  However, it is at the least a clearly defined and objective process.  I wouldn't advise investing your whole nest egg in anything based just on this, but I do think that it is relevant information." a)  Are there any predictive factors for the success/failure of your trades. i.e. Volatility has some predictive power on the failure  of the trades, therefore, you may want to fine tune the strategy such that when vol &gt; x, it stays out (or even reverses).  b) i'll make a quick subreddit. You can't tell for sure.  If there was such a technique then everyone would use it and the price would instantly change to reflect the future price value. However, trade volume does say something.  If you have a lemonade stand and offer a large glass of ice cold lemonade for 1c on a hot summer day I'm pretty sure you'll have high trading volume.  If you offer it for $5000 the trading volume is going to be around zero. Since the supply of lemonade is presumably limited at some point dropping the price further isn't going to increase the number of transactions.   Trade volumes reflect to some degree the difference of valuations between buyers and sellers and the supply and demand.  It's another piece of information that you can try looking at and interpreting.  If you can be more successful at this than the majority of others on the market (not very likely) you may get a small edge.  I'm willing to bet that high frequency trading algorithms factor volume into their trading decisions among multiple other factors. yAnother potential tool for you would be a Monte Carlo Simulator.   here's one  http://financial-dictionary.thefreedictionary.com/Business+Fundamentals I know that past performance is no guarantee.....  but I think it's in many cases not exactly a flawed tool, and especially with respect to money managers a good way to find good ones.  If a manager has shown an ability over time to consistently beat the market, yes he might be due for a bad day, but you'd generally expect that they should be able to continue that trend. I'd apply the same logic to pundits.  If their track record sucks, and they constantly seem to whipsaw you with their advice, why listen to them other than Yes it is possible but with a caveat.  It is a pattern that can be observed in many lightly traded stocks that usually have a small market cap.  I am talking about a stock that trades less than 2,000 shares per day on average. You can have a pretty good guess by looking at price pattern and order flow (size of the trades) a) price should be traded in a range b) relatively large size orders, speed.