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2 way anova jmp3/28/2023 ![]() So why no three way interaction? The factorial combination of sample Method and chemical draw out a 2x3 = 6 cell design, so at each level of well you need at least 6 observations to estimate that structure. If you use one of these macros you will have an additional effect (the three way interaction) that you can't estimate, so you can simply delete it from the model effects list. Since that's the case you can select all three variables in the list on the left of fit model, then go to "Macros" and select "Full Factorial" or "Factorial Sorted" - the latter is my preference because it groups the terms starting with lower-order effects first. In your case you have nearly a three way factorial - you're missing only the highest order interaction. To define an interaction you can select a source in the model effects and another variable in the cols list to the left, then click "Cross". This is like what Jeff showed above but with the interactions you can estimate. Sample Method, Chemicals, Sample Method x Chemicals, Well, Well x Chemical, Well x Sample method (but not the three way interaction, since that is not estimatable unless you have a full replication of the within-well factorial). The largest model would include as factors: This means certain additional terms are estimatable. ![]() It sounds like sample method and chemicals are measured factorially, which means for each Well you actually have 2 observations for each chemical, and 3 observations for each sample method (the hidden replication of a factorial design). ![]()
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