ANOVA plots

Psych

New Member
#1
Hi all,

Last minute stats exam panic....

In a 'theory' question we could be asked to give example plots for ANOVAs where:

There is/isn't an interaction (I already know no interaction would have parallel lines)

There is a main effect for variable A but not for B (or vice versa)

Just can't get my head around what these would look like - any suggestions where I could find these graphs so I can just learn them (understanding would be a bonus at this stage!)

Thanks in advance...:confused:
 

JohnM

TS Contributor
#2
For main effects:

(1) if there's no main effect, the line is basically straight
(2) if there is a main effect, the line has a slope to it

For interactions:

(1) if there's no interaction, the lines are parallel
(2) if there is an interaction, the lines are not parallel (and may cross, within the boundaries of the study or experiment)

Here's a link to some interaction plots:

http://faculty.vassar.edu/lowry/ch16pt1.html

http://psych.rice.edu/online_stat/chapter12/multiway.html

this one has some main effects as well:

http://faculty.vassar.edu/lowry/ch16pt4.html