My variables are categorical, X1 has 2 levels and X2 has 2 levels.
Is it correct to say "X1 level 1 has interacted with X2 level 1 to result in highest DV score?"
As far as I understand, it is only correct to say X1 has interacted with X2, because it is the variable and not the levels that have interacted?
Kindly enlighten me, thank you!
Two variables interact, not their levels. Interaction means that through different levels of one of your interacting variables, the other interacting variable behaves differently (namely its effect on the DV changes).
In your terms, the effect of X1 at X2's first level is not the same as the effect of X1 at X2's second level.
Two variables interact, not their levels. Interaction means that through different levels of one of your interacting variables, the other interacting variable behaves differently (namely its effect on the DV changes).
In your terms, the effect of X1 at X2's first level is not the same as the effect of X1 at X2's second level.
You and Mehmet are correct to say interaction occurs with variables and not level. However, the direction of interaction can be discussed separately. So if level 1 of each combine to give the highest that can be subsequently discussed as the nature of how variables interact can be of value scientifically.
To follow up on James answer, The information he is talking about can be found in an interaction plot. See Lawson, John, Design and Analysis of Experiments with R, CRC Press sect. 3.3. Best wishes
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