PDA

View Full Version : 2 x 4 Factorial Design and contrasts...



flanger
11-30-2008, 05:40 PM
Question...
I have a 2 (gender) x 4 (Drug Dose) design
Gender
- Male
- Female
Dose
- 200
- 400
- 600
- 800

I want to compare the two low groups together between male and female. (I want the two lower groups to be treated as the same group and the higher groups completely ignored) Is there any way to do this. Should I run contrasts? If so, are there any suggestions on to run this in SPSS?

- Thank you so much!

danielkeeton
11-30-2008, 09:38 PM
You can select cases to include or exclude those above or below the desired thresholds. For example, exclude cases where variable x is greater than or equal to 300. This would eliminate those with doses at 600 and 800 leaving 200 and 400. Then you can "flip" the data by selecting out those below and analyze those at the 600 and 800 dose. Does that make sense?

Wait are you saying you want the 4 dose measures (i.e. 4 levels) transformed to one IV with only 1 level (200 and 400 as one)? Or did you want to perform a 2x2 using dosage as IV. This is a bit different than what I mentioned above. In that you can simply go to Transform - Visual Binning then break your variable into respective parts. Or you can do a median or mean split the hard way and recode them into categorical variables 1=200 & 2=400. I am sure I my explanation is confusing as hell. I tried :D. Much easier to perform than to explain.

flanger
11-30-2008, 10:37 PM
Thank you! That actually really helped. When you stare at data for 10 hours straight, I guess you just forget the simple things. I was trying to make it WAY more complicated than it actually was.

I was talking about both the gender and dose as being IVs and running a 2 x 2. The DV is a behavioral measure.

I just temporarily excluded the higher doses for the ANOVA and it worked great! Thanks again for your advice.

- flanger