The market has handed investors some nice, consistent returns over the long run, but in the short term, it can often be as unpredictable as an episode of "The Real World." In a pair of articles, I explored the market's so-called "fat tail" distribution -- the tendency of stocks to make huge moves that seem extremely statistically improbable. Since then, I've been following "5-sigma moves," or one-day price moves that are five standard deviations or more from a stock's average one-day change.

Keep in mind that we're looking at the price change relative to the stock's historical volatility, and not just the same old jittery "most active" stocks. So even though a lot of the hottest Chinese stocks like CDC, Trina Solar, and The9 Limited saw a big drop last week, you're not going to see them on this list because of their higher average volatility.

Here's a taste of a few of the 5-sigmas from the past week:





Sun-Times Media Group (NYSE:SVN)




Valhi (NYSE:VHI)




Fremont General (NYSE:FMT)




Companhia Vale do Rio Doce (NYSE:RIO)




RadioShack (NYSE:RSH)




Sources: Yahoo! Finance, author's analysis.

As I've mentioned in prior articles, working with these stocks isn't as easy as selling every stock that makes a big move up or buying every one that does the opposite (or vice versa). Some stocks continue on a major upward march even after a huge one-day move, and some continue to lose ground even after a huge one-day fall. So you need to dig in and figure out whether the move was a result of market overreaction or of some lasting, fundamental change at the company.

Who loves the sun?
In a week when most investors were seeing red, Sun-Times was headed up in a big way. Sun-Times, the media holding group formerly known as Hollinger International, owns the Chicago Sun-Times. Its stock jumped 36% last Thursday, apparently on the back of a press release saying an unnamed foreign tax authority had given the company "a favorable review on a foreign tax matter." The company was sparse on specifics and said it would not be reversing any foreign tax accruals at this time.

It could probably be argued that Sun-Times investors have been looking for even a faint glimmer of good news, since the company has been roiled in controversy and the stock had fallen more than 50% before last week's big jump. As of the end of the quarter ending in September, Sun-Times had $594 million of tax-related liabilities, the majority of which was set aside as contingent on certain tax rulings. While the favorable ruling could mean a small windfall for Sun-Times, the press release struck me as a bit vague to throw a party over.

After the markets closed last Thursday, Sun-Times also released an 8-K saying that a special committee appointed by the board had concluded its investigation into options backdating at the company, and found that some options awards had been backdated between 1999 and 2002. Surprisingly, the company did not accompany the 8-K with a press release. The following day, the company filed to delay the release of its 10-K, since it has turned its resources toward restating past financials to adjust for the backdated options.

The report is only the latest blow to Sun-Times, which, when it was still Hollinger, had been thoroughly dragged through the muck by its former CEO, Lord Conrad Black. Black had taken it upon himself to use Hollinger as his own personal piggy bank - for example, spending $9 million of the company's money on Franklin Delano Roosevelt memorabilia to decorate his Palm Beach and New York homes.

The resolution of the stock-option backdating issue could be another step on the road to recovery for the company. But even with a clean slate, it must still contend with the tough business environment plaguing competitors like Tribune.

Read up on some more Foolish coverage of last week's dive:

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Fool contributor Matt Koppenheffer enjoys his weekly statistical rendezvous even more than he likes watching the crazies duke it out on "The Real World." He does not own shares of any of the companies mentioned. The Fool's disclosure policy loves you even when your stocks are down.