Thorns, if your system is based on statistics, then you have to use stats. and use as many races as you can to see if it's profitable .

On the other hand, if you base your system on form and handicapping, then it's easy to check if it was coincidence-luck whatever.

Your selections based on your system have to be consistently in the first four or five placegetters. ("consistently" doesn't, mean in every race, just most) that would assure you, to get a first selection strikerate you are talking about.