On Mon, 18 Feb 2002 20:57:36 +0100, "jan plessers" <[EMAIL PROTECTED]> wrote:
> Hello, > > I did a likert on 2 groups, a Mann-whitney showed that ther was a > significant difference between the 2 groups. If 'did a Likert' means what I expect, and the scaling was decent enough to be worth commenting on, then the rank-transformation was unneeded and wasteful of information. > The next thing I did were some > univariate statisics between the covariates and I found some significant > differences between the covariates (ex. age sign. differs between the 2 > groups). > My questions are: > Can I test again for a sign. difference between the 2 groups, but with the > covariates controlled ? How to do this? How to do this in SPSS ? If the groups aren't random, and especially when they are non-randomly non-random, then you have to build the argument that covariates don't matter. First, you can stick them in and see if anything changes. If not, then you are okay. You do want to ask the procedure to interpret the covariates 'before' or 'at the same time as' (not, 'after') the main effects. I've always done this in SPSS (6.1 and earlier) with ANOVA vara by grps(1,4) with covar/ -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at http://jse.stat.ncsu.edu/ =================================================================
