As a graduated psychology student, I can tell you how my professor did his statistics classes:
He was almost desperate because of the small percentage of students who seemed to grasp what he was teaching.
I mean, a lot of psychologists are really 'out there' (I'm a psychologist myself, so I'm allowed to make this statement :-)
So he used any visual aid a man can think of: puppets, jars with marbles, excellent chalking skills on a blackboard,...
That worked very well!
For a small percentage of the students, it was kinda infantile. But for the major part, this approach was really necessary!
You have to know that lots of psychology students think there's no place for 'hard' science in psychology. They couldn't be more wrong of course (as they will also have to learn genetics and some basic neurology).
Now, I don't know if they are freshmen or not ,but in the former case an extensive approach may be necessary. For senior students, well, teach like you already do. They now how to handle it, or at least they should.
Oh yeah, it's already mentioned before, but please: do point out the difference between correlation and causality!