what is the residual sum of squares rss 
the residual sum of squares rss is a statistical technique used to measure the amount of variance in a data set that is not explained by a regression model itself instead it estimates the variance in the residuals or error term linear regression is a measurement that helps determine the strength of the relationship between a dependent variable and one or more other factors known as independent or explanatory variables understanding the residual sum of squares rss in general terms the sum of squares is a statistical technique used in regression analysis to determine the dispersion of data points in a regression analysis the goal is to determine how well a data series can be fitted to a function that might help to explain how the data series was generated the sum of squares is used as a mathematical way to find the function that best fits varies least from the data the rss measures the amount of error remaining between the regression function and the data set after the model has been run a smaller rss figure represents a regression function that is well fit to the data the rss also known as the sum of squared residuals essentially determines how well a regression model explains or represents the data in the model 