I am sure that everyone who's trying to find patterns in historical stock market data or betting history would like to know about this. Given a huge sets of data, and thousands of random variables that may or may not affect it, it makes sense to ask any patterns that you extract out from the data are indeed true patterns, not statistical fluke.
A lot of patterns are only valid when they are tested in the samples. And even those that are patterns that are valid out of samples may cease to become valid when you apply it in the real world.
I understand that it is not possible to completely 100% make sure a pattern is valid all the time, but besides in and out of samples tests, are their any tests that could establish the validness of a pattern?