Define simple effect (sometimes called simple main effects). How would you calculate them?

Define simple effect (sometimes called simple main effects). How would you calculate them?



THE SIMPLE PICTURE OF JUST MAIN EFFECTS
If you do get a significant interaction, you can find out what is happening in each of your conditions by analysing the simple effects. Where you find a difference between simple effects, you have spotted an interaction!

*Simple effects show the difference between any 2 conditions of 1 IV in one of the conditions of the other IV **

Simple effect analyses are equivalent to t-tests, but involve the calculation of F values, and you can get SPSS to calculate them for you, but this is v complex, so instead, use t-tests!!


Simple effects= a comparison of two cell means of 1 IV, within one condition of another IV (see diag!)

The more simple effects you calculate, the higher your family wise errors will be.
You should therefore be selective in your simple effects calculations:

Your hypothesis(prediction about how cell means will differ (based on previous lit)) should guide which simple effects calculations you conduct (a priori comparisons, but using t-tests!) If your comparisons are post hoc (or a priori, but using t tests and making many comparisons) then use Bonferroni's correction!

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