Introduction to Assessing the Fit of a Line

What you’ll learn to do: Use residuals, standard error, and r² to assess the fit of a linear model.

Graphing the regression line with the scatterplot gives a visual depiction of how well the regression line fits the data.  To further hone in on assessing the fit of our regression line to the data, in this section we present:

• Residual plots.
• The correlation coefficient r gives us a numerical way to measure this fit.
• Interpreting the square of the correlation coefficient r² .
• Interpreting the standard error s_e.