When dealing with factorial experiments, we can ask two questions:

• is there a main effect?
• what is the interaction?

Going back to the keyboard example (factorial-anova), is there a main effect on WPM overall when sitting or standing. And is there an interaction between these two? E.g. would posture differentially affect the performance on keyboard?

References

• anova-assumptions
• one-way-anova
• analyzing-a-factorial-anova