Frankly there's not much gleaned from stock prices over a short term
It's easy to disprove that. If it were to hold true, a "buy if the price is below the 100-day-mean, sell if above" would be profitable. And that approach would be exploited to the extent that this pattern goes away.
You're talking about an individual stock price. I'm talking about the market.
Put another way, your strategy completely works because stocks (as a market) trend upward. You'd want to better define "above" and "below" (because, transaction costs) and you'd also want to consider the period (100 days).
