> Anders D Hojen wrote: > > Hello, I just joined this list - hope somebody can help me with this > question. > I have a 2-way anova with one within- and one between-groups measure. > There is a confound between the 3 levels of the within-groups measure > that I can get rid of by converting to z-scores. However, If I > standardized the three levels of the within-groups measure, the mean > for all levels will, of course, be 0 in all 3 cases. This means that > the main effect of this factor is neutralized. That is actually a good > thing because I am only interested in the between-groups factor and in > the interaction. My question is whether it is legitimate to do this.
Legitimate in what sense? In practice, this kind of analysis is common and won't be a problem for ANOVA. The F ratio for the factor you are not interested in is artificially low (but for obvious reasons). The main thing is to explain the procedure and reason behind it clearly (and concisely). > There seems to be no point in standardizing all scores - I don't > get rid of my confound and the ANOVA turns out basically the same as > the ANOVA on raw data. Hope you can help. Depending on the nature of the confound there may be a more obvious/natural transformation than the z score. Thom . . ================================================================ This list will soon be replaced by the new list EDSTAT-L at Penn State. Please subscribe to the new list using the web interface at http://lists.psu.edu/archives/edstat-l.html. ================================================================
