S, R and adjusted R are measures of how well the model fits the data.

·    S is measured in the units of the response variable and represents the standard distance data values fall from the regression line. For a given study, the better the equation predicts the response, the lower S is.

·    R (R-Sq) represents the proportion of variation in the observed response values that is explained by the predictor(s).

·    Adjusted R (R-Sq(adj)) is a modified R that has been adjusted for the number of terms in the model. If you include unnecessary terms, R can be artificially high. Unlike R, adjusted R may get smaller when you add terms to the model.

For the particleboard data, the S is 8.86937 units of stiffness. Additionally, 84.5% of the variation in stiffness is explained by density. The adjusted R is 83.9%.