Residual Sum of Squares

The residual sum of squares (RSS) is calculated as the sum of deviation Squares.

If the experimental data y_j measured at the points x_j for the curve i, and the model function f(x) is calculated at these points, then the regression values are f(x_j).

The residual between the experimental value and model value for i^th curve isy_i,j – f(x_i,j).

The Sum of the Residual Squares is

If the model curve is drawn exactly through the experimental points, then all Residuals are zero and RSS is zero too.

The closer the calculated model curve is to the experimental data, the closer is RSS to zero.