ANOVA Assumptions

One-way ANOVA is justified by three core assumptions:

  • an additive model
  • independent observations with common variance
  • normally distributed errors

These assumptions are checked with residual diagnostics rather than from the ANOVA table alone.

R

fit <- aov(y ~ treatment, data = dat)
plot(fitted(fit), resid(fit))
qqnorm(resid(fit))
qqline(resid(fit))