WESTCHESTER COUNTY, N.Y. (TheStreet) -- The media is, by and large, telling us to buy the new iPhone, but stay clear of Apple (AAPL) stock in the wake of today's iPhone 5 launch.They are basing their advice on historic price movements after iPhone launches. How vast is the sample size? You didn't really ask that, did you? Since 2007, there have been (count 'em) four iPhones. No matter. The New York Post writes with emblematic certainty. Its sub-headline echoes the headline: "Buy phone, not stock, Apple shares dip following gadget intros"Just in case you were slow on the uptake, it was repeated in the lead: "It's Apple-bobbing season. Investors are hoping for a share boost from the tech giant's much anticipated iPhone 5 unveiling today, despite a history of post-launch lulls in the stock price." Soon we hear how: "Apple's stock has dipped in the first 30 days after every major product launch since in 2008." That means, of course, excluding the first iPhone. So, depending on your time frame, (mid-to-long term the stock ran skyward after all these launches) Apple's stock did alright after one iPhone launch, disappointing after three. Make one shift in the statistical sample, and, well, we're all even. Look: from a larger perspective, stocks are anticipatory mechanisms. It makes some sense that they might run up before an exciting product launch, giving back a portion of the gains afterwards. But acting on hard and fast rules from such a small, fallible sample size of four is a one-way ticket to financial Palookaville.