Let me just rewrite the formula here just to remind you. It was literally the mean of the products of each of our data points, minus, or the XYs, minus the mean of Ys times the mean of the Xs. All of that over the mean of the X squareds, and you could even view it as this, over the mean of the X times the Xs, but I could just write the X squareds over here, minus the mean of X squared. This is how we figured out the slope of our regression line. Or maybe a better way to think about it, if we assume in our regression line that the points that we have were a sample from an entire universe of possible points, then you could say that we are approximating the slope of our regression line. You might see this little hat notation in a lot of books. I don't want you to be confused.