- Residual plot - Glossary Term
A residual plot is a scatterplot with the residual values shown on the vertical axis and the explanatory variable shown on the horizontal axis. Residual plots are useful in assessing the fit of the statistical model (e.g., by a least-squares line).
When the least-squares line captures the overall relationship between the response variable y and the explanatory variable x, the residual plot will have no clear pattern (be random) see opposite. This is what is hoped for.
scatterplot with least squares line
If the least-squares line fails to capture the overall relationship between a response variable and an explanatory variable, a residual plot will reveal a pattern in the residuals. A residual plot will also reveal any outliers that may call into question the use of a least-squares line to describe the relationship. Interpreting patterns in residual plots is a skilled art and is not required in this curriculum.