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 MeadWestvaco (NYSE:WRK) jumped 12%, after the company got a big new investor.

So what: Nelson Peltz's Train Fund Management said that it has about a 1% stake in the company, in a regulatory filing made Thursday. The fund owns 1.6 million shares in the company.  

Now what: Big investors buying a stock don't fundamentally change a company, but they can be a bullish indication for traders. I don't think it's worth buying just because someone else is, especially without significant news. I'd stay away from the move for today and, if shares pull back from this pop, it would be a better time to jump in.

Interested in more info on MeadWestvaco? Add it to your watchlist by clicking here.