* data for parts (a) and (b);
data sales1;
 input treat store time1 time2; sales=time2-time1;
 datalines;
 1     1  69.7  72.2
 1     2  74.3  72.2
 1     3  74.4  71.7
 1     4  77.7  73.7
 1     5  72.7  74.4
 2     1  76.3  83.7
 2     2  71.9  83.8
 2     3  71.7  87.2
 2     4  72.7  89.6
 2     5  66.4  78.3
 3     1  74.5  92.5
 3     2  71.4  89.7
 3     3  69.4  86.4
 3     4  73.9  86.2
 3     5  77.1  90.4
;

* data for repeated measures over time, part (c);
data sales2; set sales1;
sales=time1; time=1; store=_n_; output;
sales=time2; time=2; store=_n_; output;
drop time1 time2;
proc print; run;

* spaghetti plot;
proc sgpanel;
panelby treat / rows=1 columns=3;
series x=time y=sales / group=store;
run;