You know some pretty smart 12 year olds who are talking about ISoP I can distinctly remember sitting in my attic with cards laid out and and subtracting AVG from SLG. The best of these would be my "Sluggers" when arranging my cards into batting orders. I had no idea it had a name, it just seemed like something worth doing. I'd also subtract AVG from OBP to "see who walked alot" amongst those with decent averages. EDIT: This may have been later. Thinking back, I imagine lots of kids did very similar things. I stand corrected if Im really in the minority with this. When I was that young my brain didn't comprehend stats beyond wins, losses homeruns, rbi's and averages