Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of private post-secondary school Education Management (Nasdaq: EDMC) are heading into graduation season on wobbly legs, posting a brief 5% gain followed by an equally quick 10.1% drop. In the end, the stock settled around 2% above last night's closing price, all on feeble trading volume.

So what: There isn't much going on in paid-education land today. Rival ITT Educational Services (NYSE: ESI) saw a similar low-volume decline, though without the severe spike-and-drop swings of Education Management.

Now what: ITT's much higher average trading volume probably saved that stock from Education Management's flailing today. Low-volume stocks are easily manipulated, whether intentionally or not, and an even lower-volume trading day just magnifies the liquidity problem. This is why we Fools always prefer set-price limit orders over more random market orders on that class of investments.

Interested in more info on Education Management? Add it to your watchlist.

Fool contributor Anders Bylund holds no position in any of the companies discussed here. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is investors writing for investors.