Your probability of flipping heads is higher than your probability of rolling 1 on a six-sided die: X = .5, Y =~ .167. I have yet to even hear of a good setup for measuring X or Y, to say nothing of actual numbers for them, for measuring "probability of success in a startup". Heck, I have never even heard a defensible universalizable definition of success for a startup.
Incidentally, and this has always bothered me about statements like "give your X the highest probability of Y": do people routinely get the opportunity to run a simple random sample of startups, marry a simple random sample of women, raise a simple random sample of children, etc? No? Then why do we bastardize statistics in this manner.