It is true that statistics reflect things that are done repeatedly. But even if we were to do it only once, it is still very helpful to consult a reliable statics before doing it, especially if the choice might have serious consequences. For example, if statistics shows going to a college right after high school will increase your chance of success significantly than not going to college right after high school. In that case, we will want to go to college. It is not saying that not going will for sure make one a failure, but the chances are different there.
It seems to me that the OPs numbers are about in the ball part right. A 10% will go bad, and a 10% will be the envy of everyone. T he rest of us is nicely distributed in the middle.
