On Nov 1, 3:10 pm, Stuart.Pal...@deakin.edu.au wrote: > [...] > > Sets A and B are cross-sectional (representative) samples of two different populations. The members of the sets at time 1 and 2 are different, though still representative. The principal measure of interest is the mean value (of a rating given by) the respective sets. > > I have used one-way ANOVA to explore the significance of the difference in mean score between A1 and A2, B1 and B2, A1 and B1 (ie, [Ma1-Mb1]), and, A2 and B2 (ie, [Ma2-Mb2]). > > My interest/question was about testing the significance of the 'difference of the differences' (Ma1-Mb1)-(Ma2-Mb2). > > I had considered a two-way ANOVA using all of the data and looking at the significance of interaction term, but was unsure. I will look at this. > > Thanks again.