The QQQ might have only a small visibile statistical ramp (you averaged all the period, take only the period when the 3:55 is higher than the 3:30 period and see what average you get), I would be surprised that if you take only that set you get less than 1% average gain for those 25 minutes.
Surprisingly, I guess for both of us, the average gain is only about 1/3 of one percent. Still, that's 10 cents on the QQQ's, so nothing to sneeze at. Still, the original question stands: what tips you off? Is there something visible, or are you just gifted?
Hard work often pays off over time,
but laziness always pays off right now.