What "likely" means

When we say something has a one-in-six chance, we are making a claim about the long run. Roll a fair die six hundred times and you should see a six roughly a hundred times — not exactly, but close, and closer the longer you go.

That is all a probability is: a number between 0 and 1 for how often something would happen if you could repeat the situation many times. 0 means never, 1 means always, and one half means half the time.

Short runs are lumpy. Ten rolls can easily show three sixes, or none. The pattern only settles down with many tries — which is why a single surprising result tells you very little.