A small disagreement with the article. Statistical arbitrage is a more general principle than "reliance on mean reversion" (though that is certainly a common example of statarb). It really encompasses any useful statistical prediction that can be used to trade with.
While I agree that the article is somewhat vague and imprecise, it is not accurate to encompass all statistical predictions as statarb either. That would more be what "quantitative" is.
For a strategy to be considered statistical arbitrage, it needs to be something _against_ something else. You can do purely directional statistical predictions, and that would not be statarb.
Very true! Though the dividing line between purely directional, and something against something else is unclear. Every price is against something else, in some sense.
