Solved – Alternative to 2-way ANOVA when variances are unequal

I'm working on a question on 2-way ANOVA where there are 2 treatments and 1 blocking factor. The residual plots suggest unequal variance. What is another parametric or non-parametric alternative method to 2-way ANOVA?

ANOVA is equivalent to regression using categorical (aka "dummy" or "indicator") variables. So any techniques from regression can also be applied to ANOVA. Here are some suggestions:

  • If the error terms appear to be normally distributed, you could try using weighted least squares.
  • If the error terms are not normally distributed, you would probably need to transform the variables.

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