Past performance of a finite sample of 28 stocks is no guarantee of future performance. It's no edge. Ever hear of the Super Bowl indicator?
There are no guarantees in trading. it's not a guarantee, it's a statistical advantage. Nobody can guarantee you it will work in 100% of weeks, but 70-80% of cases should be good enough assuming the data is correct.
It isn't an edge or a statistical advantage. I could arbitrarily pick any useless canned indicator (RSI, MACD, Stochastic, Commodity Channel Index, whatever) and run it against the universe of optionable stocks for a given time period and cull out the ones that yielded a 100% gain while the market did 20%. I guarantee you that going forward you would have hardly any chance of duplicating that 100% performance and just as good a chance of losing money. It's no more than curve fitting.