And when you say probability, it's really just a way of measuring the likelihood that something is going to happen. And the way we're going to think about it is how many of the outcomes from this trial, from this picking a marble out of a bag, how many meet our constraints, satisfy this event, and how many possible outcomes are there? So let me write the possible outcomes right over here. So possible outcomes. And you'll see it's actually a very straightforward idea, but I'll just make sure that we understand all the words that people might say. So the set of all the possible outcomes, well, there's three yellow marbles, so I could pick that yellow marble, that yellow marble, or that yellow marble. These are clearly all yellow.