It can only take on a finite number of values, and I defined it as the number of workouts I might do in a week. And we calculated the expected value of our random variable X, which you could also denote as the mean of X, and we used the Greek letter mu, which we use for population mean. And all we did is it's the probability weighted sum of the various outcomes. And we got for this random variable with this probability distribution, we got an expected value or a mean of 2.1. What we're going to do now is extend this idea to measuring spread. And so we're going to think about what is the variance of this random variable, and then we could take the square root of that to find out what is the standard deviation. The way we are going to do this has parallels with the way that we've calculated variance in the past.