What are the benefits of using factorial ANOVA designs?

What are the benefits of using factorial ANOVA designs? 



Factorial designs can test the effect of 2 or more FACTORS on 1 DV at the same time.

Enables us to find out if there is an INTERACTION between the two factors!

1)Two factor design moves one step closer to reality- testing the effects of two IVs on a DV simultaneously.
[Manipulation of a single IV with all other variables held constant is criticised for its extreme separation from reality- in life we are affected by several influences together at any one time].

2) By manipulating more than one factor in an experiment, we get to see the ways in which one factor INTERACTS with another
E.g. comparing effects of caffeine on driving performance, against placebo, after five hours' sleep and after none. (2X2 DESIGN)

3) Use of two factors is often demanded by the research question, but often simply convenient- two experiments in one, plus the interaction effects. E.g. Coffee on driving, sleep on driving, and interaction between the two.
4) Statistically: type 1 errors are more efficiently accounted for than they would be by running several experiments each with a .05 probability of type 1 error.

Overall, can help us discover more general, nuanced principles e.g. After five hours sleep caffeine improved performance, compared with the placebo for a full two hours of driving, whereas after no sleep, caffeine only improved performance for the first 30 minutes, but performance deteriorated markedly after that.

Can draw out more useful general/applicable conclusions from this/ factorial designs!

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