I used this: emmeans::emmip(mod, Behandlung ~ Ernte|Genotyp) to get my plot, thanks to Russ Lenth.

What can I see?

What I think I can see: an interaction of Bahandlung K with TS in both genotypes. Am I right?

Thank you for your help.


1 Answer 1


I don't agree with your use of the technical term "interaction". It is factors that interact, not their levels.

It's easier to describe the results without that term anyway, and instead describe the patterns in the means.

  • The most notable pattern is that when Ernte is 2, you get the same response, about 95, regardless of the other two factors.
  • When Ernte is 1, then (compared with Ernte 2)
    • you get a somewhat higher mean response, about 98, when Behandlung is K, about the same regardless of Genotyp.
    • you get a lower mean response when Behandlung is TS, but how much lower depends on Genotyp. It is drastically lower with Genotyp WT

If you do want to use the term "interaction", I'd put it this way.

  • Look at the left panel alone. There, you see a two-way interaction between Behandlung and Ernte. That is true because the effect of Ernte is different for each of the levels of Behandlung.
  • If you look at just the right-hand panel, you also see a two-way interaction between those factors. But that interaction is much stronger than in the left panel.
  • The fact that these two-way interactions are not the same is why there is a three-way interaction.

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