Trend Analysis Question

#1
Hi There,

I have a very quick question about trend analysis. I have a data set where there's two IVs: Drug and Task. Both variables have three levels. I've found a significant interaction. There's also a significant interaction when I add a test of some pre-study abilities as a covariate.
My question is... would it be appropriate in SPSS to see if there's significant linear or quadratic trends of the IVs? I'm just a little shaky on when, in general, you'd want to do trend analysis. Thanks! :)
 

JohnM

TS Contributor
#2
You can do a trend analysis whenever it "makes sense" - i.e., the IVs are either ordinal or interval/ratio and can be described as increasing or decreasing amounts.

...and you should do it whenever the research questions / objectives call for it.