All right, so let's just make sure we understand what is going on. So let's first think about the population. So I'll do that right over here. So in the population, there might be some true linear relationship. So in theory, on our x-axis, we would have our reaction time, and on our y-axis, you have your memory time. If you were able to plot every single possible data point, it might even be an infinite or near infinite, so it would be very hard to do it, but if there was just some truth in the universe that says, yes, there actually is a positive linear relationship, and it looks like this, and you could describe that regression line as y hat, it's a regression line, is equal to some true population parameter, which would be this y-intercept, so we could call that alpha, plus some true population parameter that would be the slope of this regression line, we could call that beta, times x. Now, we don't know what this truth of the universe is, of the linear relationship between reaction time and memory time, but we can try to estimate it, and that's what Jian is trying to do.