What is the explained sum of squares?
The “Sum of Squares” is a mathematical way to minimize the average overall deviation of a set of points from a mean value.
The term is derived from the equation used to optimize or minimize the average overall deviation of a set of points from a mean value, which is usually a regression line or curve in statistics. Using the square of the difference between individual points and the calculated mean point gives us a measure of the relative “fit” or agreement of our calculated regression line to the actual data that is always positive. Thus the “fit” of the line, and therefore its usefulness as a predictive or descriptive function are easily seen by how small this term is for any data set and regression curve.