A buying strategy

Somebody wrote and asked about some Gil Blake method for buying and selling. Of course, I had never heard of the guy ... but I did find these comments by Blake: "If the Dow climbs 10 points, what's its expected further excursion before reversing?" and "... once they've gone, say, 1 percent in one direction, they're likely to go 2 percent further before they go back again." Huh? Is that true? So I decided to check out that observation by looking at, say, GE stock. Well, not exactly that observation. I looked at the total gain over a moving n-day window. When the gain exceeded 1%, did the gain for the (moving) time period continue to increase? If that happened most of the time, then should one buy when that occurs? Would that be following some "trend"? But what's a good value for n? Should we look at the gain over a window of n = 3 days or maybe n = 4 days ... or what? Anyway, to make a long story short, I got some charts that look like this: Now I gotta massage that spreadsheet. If we see a nice n-day gain, how much more can we expect? Click for a pretty picture.