This column was originally published on RealMoney on Sept. 28 at 4:00 p.m. EDT. It's being republished as a bonus for TheStreet.com readers.Exchange-traded funds are different from typical index funds and much different from actively managed open-end funds. ETFs are index funds that trade throughout the day like a stock, while OEFs price once a day after the stock market closes. One more important difference: ETFs are very new, which means that many do-it-yourselfers do not know much about them and many investment professionals and market-related Web sites still are learning how to analyze them properly. While I may or may not know the best way to analyze ETFs, I sure do know a bad way to analyze them: to look at ETFs as if they were OEFs. An investor who wants to buy an actively managed OEF may find that there's not much to analyze, because that investor is really buying the manager's past performance on faith that that past performance can be maintained. Some bets, like Bill Miller, are better than others. Obviously, there's more to fund selection than this, but ultimately, it comes down to a belief in the manager.