Re: Difference Score as a dependent variable

Posted by Bruce Weaver on Apr 17, 2014; 5:38pm
URL: http://spssx-discussion.165.s1.nabble.com/Difference-Score-as-a-dependent-variable-tp5725496p5725504.html

Thanks for clarifying.  Following up on Art K's earlier post, One option would be a 5 (between-Ss) x 2 (Within-Ss) mixed design ANOVA.  The "reality TV" question gives you 5 independent groups.  The 2 paired scores are the means of the appearance and competence items respectively.  The model term of most interest to you is the interaction term.  The F-test for the interaction tests the null hypothesis that the difference between appearance & competence means is the same for all 5 "reality TV" groups.  Given that the groups are ordered, the default polynomial contrasts you get (with GLM) would be appropriate for the main effect of Group and for the interaction term.  

Note that if you ran a one-way ANOVA (with the 5 groups) using the difference scores as the outcome variable, the F-test for Group in that one-way ANOVA would be identical to the F-test for the interaction in the mixed design ANOVA described earlier.  This makes sense, because the null hypothesis for the one-way ANOVA is that the differences are not dependent on group.

HTH.

Laura2014 wrote

The media variable is "watching reality TV" and is measured by asking respondents to indicate on a 5-point scale (ranging from never to every day), how often they watch reality TV?
Thanks!