A good first step would be to combine all 3 years into 1 dataset. You could do this using the (in=) dataset option. data all_years;
set survey2012(in=s12) survey2015(in=s15) survey2018(in=s18);
if s12 then year = 2012;
if s15 then year = 2015;
if s18 then year = 2018;
run; Because you have discrete responses (1, 2, 3, or 4), comparing the medians of the groups rather than means might be a good option. A Kruskal Wallis test would achieve this and can be done in SAS using proc npar1way. In your case, the variable after "class" is the grouping variable (the year of the survey). The variable after "var" is the variable we want to compare across years (score). proc npar1way data=all_years;
class year;
var score;
run; More info on using the npar1way procedure can be found here.
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