Checking an analysis-of-variance model
Section of Analysis of variance examples, part of Data analysis
Checking an analysis-of-variance model
| Type | Section |
| Taught in | Analysis of variance examples |
| Part | Data analysis |
The F test assumes independent normal errors with the same variance in every group. These are checked through the residuals, y_{ik}-\overline y_{i\cdot}: a plot of residuals against fitted values should show no pattern and similar spread in each group, and a normal quantile plot of the residuals should be close to a straight line.
plot(coldsore.lm, 1:2) # residuals against fitted values, and a normal Q-Q plotIndependence is not something a residual plot can verify. It comes from the design: here, from assigning treatments to separate patients at random.
Used in
See also
Bonferroni correction · Interaction · Which groups differ? · Two-factor analysis of variance · Randomisation and blocking · Main effect