This is close to the best calculation, the best estimate that we can make, given the data we have. And sometimes this will be called the sample variance. But it's a particular type of sample variance where we just divide by the number of data points we have. And so people will write just an n over here. So this is one way to define a sample variance. In an attempt to estimate our population variance. But it turns out, and in the next video I'll give you an intuitive explanation of why it turns out this way.