Here’s the basic idea: The closer the line is to all of the data points, the better the line summarizes the pattern in the data. The length of each vertical line segment is the amount that the predict...Here’s the basic idea: The closer the line is to all of the data points, the better the line summarizes the pattern in the data. The length of each vertical line segment is the amount that the predicted y-value deviates from the actual y-value for that data point. The most common measurement of overall error is the sum of the squares of the errors, or SSE (sum of squared errors). When we compare the sum of the areas of the yellow squares, the line on the left has an SSE of 57.8.
