Recently, in "Painfully Obvious Stock Tips," I described how beating the average performance of the market is a simple matter of eliminating "bad" stocks and choosing from among the "good" ones that remain. Throw out the companies that perform "worse than average," pick only from the ones that do "better than average," and voila! You're likely to earn better-than-average returns.

Today, I want to expand on that concept -- but only a little. If you're a statistics major, if your idea of an enjoyable way to spend an evening is doing calculus problems for fun, this column is probably not for you. Because I'm going to keep this really simple.

David vs. Goliath, Inc.
Let's get one thing out in the open right away. In the quest for superior, market-beating investment returns, individual investors are at an apparent disadvantage to the professionals at huge investment houses like Merrill Lynch and their seemingly unlimited resources.

The good news is that you don't need all of the trappings of an investment bank to perform like one -- or better. You can get by without the interns, the proprietary data feeds, and, yes, the fortune-tellers, too. Because they simply aren't necessary to beat the market. Don't believe me? Take a look at the returns we've been racking up at Motley Fool Hidden Gems over the past two-plus years. In the 2003 bull market, in the secular bear of 2004 and 2005, and the crazy market of today, we're continuing to beat the pants off the S&P 500 by a margin of, at last count, 27% average returns, compared with 6% for similar amounts invested in the index.

And how do we do it? By focusing on what's important. By filtering out the noise. By concentrating on just a very few simple factors that help us to eliminate losing investment ideas and choosing only from among the likely winners.

Trying too hard
I recently read a research report from one of Wall Street's premier investment houses. Fourteen pages long, it crunched price-to-earnings (P/E) ratios, returns on equity and investment, calculations of market size and penetration, analyses of suppliers' pricing power, and on and on, ad nauseam. The analyst who prepared the report must have put hundreds of hours into its preparation, trying to cover every conceivable angle. But was all of that effort rewarded? Did his painstaking efforts to nail down an accurate valuation of the company, 12 months in the future, pay off?

Not really. His price target, due to arrive a year off, was never hit, and now the stock has dropped down to where it was back when the report was published.

That company was Cisco Systems (NASDAQ:CSCO), a heavily followed and well-known stock. With the stock trading around $19 in June 2005, CIBC World Markets published a $25 price target, predicting faster-than-expected growth, greater global IT spending, and integrated partnerships with firms such as IBM (NYSE:IBM) and Tibco Software (NASDAQ:TIBX).

National Bank Financial was also bullish on Cisco, offering a price target of $24. Analysts there saw a cash machine that would grow with the expansion of IP and strengthen relationships with operators such as Vodafone (NYSE:VOD).

And then there was JPMorgan, which called Cisco fairly valued at $19 because it saw orders softening at Cisco suppliers Xilinx (NASDAQ:XLNX) and Altera (NASDAQ:ALTR), a seasonal sales decline forthcoming, and a multiple-based valuation that looked fair compared to peer Juniper Networks (NASDAQ:JNPR).

What's happened? Cisco flirted with $22 back in March but has since come back to $19. Kudos to JPMorgan for being the closest in this game, but as the saying goes, "Performance may vary." It seems as though these analysts are going to an awful lot of effort to forecast prices one year out -- and missing the mark.

The CIA on investing
So with all of their resources, and with all the time they put into valuing these companies, why aren't the "professionals" producing more accurate results? A 1973 report written by analyst Richards J. Heuer at the CIA (yes, that CIA) suggests one answer. In his study, several of the people who set the odds on horse races were tested to determine whether having more information resulted in making better predictions on race winners. Given 88 pieces of data to choose from, the handicappers, as they're called, were told to choose the five bits of information they considered most important (e.g., the horse's win-loss record, the jockey's record, the length of the race, and so on). They were then asked to place bets on a race based on their preferred data and to state how confident they were of their predictions.

In part two of the test, researchers doubled the amount of data given to the handicappers. They got their "preferred five" pieces of data, plus five more statistics that they considered of lesser importance. Bets were again placed. Confidence was remeasured. This test was repeated with 20 and then with 40 statistics to work from.

The researchers then analyzed the results and concluded that the handicappers' accuracy did not improve as they were given more and more data. In fact, several handicappers got worse the more data they were fed. But while the accuracy of their predictions didn't increase with the amount of information they had to work with, their confidence in those predictions did. This was despite the fact that, by their own admission, the extra data was not as useful to them as the original "preferred five" pieces of information.

Henry David Thoreau on investing
All of which suggests that Henry David Thoreau was right. If you recall from your high school American Lit class, in Walden, Thoreau wrote:

Simplicity, simplicity, simplicity! I say, let your affairs be as two or three, and not a hundred or a thousand; instead of a million, count half a dozen, and keep your accounts on your thumb nail. ... Simplify, simplify.

Is it a coincidence that Thoreau urged limiting our focus to "half a dozen" things at a time, and that the handicappers picked just as many winning horses with five pieces of essential data as they did with those five plus 35 others? Perhaps. But coincidence or not, it works.

Because when you see a company selling for 100 times earnings and growing at 10% a year, you don't need a research staff to tell you it's overpriced. On the other hand, when a company sells for 10 times free cash flow, grows profits 25% per year, and is managed by seasoned, conservative management, you know that's a company worth investigating. You need to only understand a few key metrics to help you separate the winners from the losers. And if you can manage that, then, yes, you can beat the averages -- and the analysts, too.

At Hidden Gems, we look for obvious winners like the one just described (incidentally, it's protective-products maker Mine Safety Appliances, and since we bought it two years ago, it's up more than 140%). It's just one of more than 50 promising stock ideas we've passed on to our subscribers over the past two years. If you'd like to see the rest, come join us at Hidden Gems for a 30-day free trial. You have nothing to lose.

This article was originally published on May 13, 2005. It has been updated.

Fool contributor Rich Smith does not own shares of any company mentioned. JPMorgan is an Income Investor recommendation. The Fool's disclosure policy is less than 14 pages long.