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 semiconductor materials supplier ATMI (Nasdaq: ATMI) dropped more than 10% on above-average trading volume this morning.

So what: ATMI's fourth-quarter numbers beat analyst expectations on sales, but needed help from a one-time tax benefit to surpass the consensus earnings target. Management characterized 2010 as a development year, which did nothing to impress investors.

Now what: Fellow chip-materials vendor MEMC Electronics Materials (NYSE: WFR) also missed analyst projections last night, but that stock is spiking today because management sees good things ahead for its solar-panel operations. ATMI doesn't have that kind of diversified operations to fall back on and is suffering the consequences today. But the stock recently carried a five-star CAPS rating (out of five) and is far more value-priced than MEMC. Buying on this weakness could be smart if this quarter's troubles turn out to be temporary.

Interested in more info on ATMI? 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.