DEFINITION of 'Residual Sum Of Squares  RSS'
A statistical technique used to measure the amount of variance in a data set that is not explained by the regression model. The residual sum of squares is a measure of the amount of error remaining between the regression function and the data set. A smaller residual sum of squares figure represents a regression function which explains a greater amount of the data.
INVESTOPEDIA EXPLAINS 'Residual Sum Of Squares  RSS'
It is not possible to draw conclusions about the correctness of the regression function solely using the residual sum of squares. Since a sufficiently complex regression function can be made to closely fit virtually any data set, further study is necessary to determine whether the regression function is in fact useful in explaining the variance of the data set. Typically, however, a smaller residual sum of squares is ideal

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