I just ran the PROC MIXED for outputting the residual error in SAS [TO CHECK FOR NORMALITY]

I am wondering if I need to look at Shapiro-Wilk or Kolmogorov-Smirnov tests? My sample size is 217 [repeated at 3 time points]. So, when I check for the normality of the residual error, do I run them separately at each timepoint or consider them all together?

Does that make a difference?

Thanks for your time.

I am new to this forum and newly using SAS, any feedback would be greatly appreciated!

Thanks,

PhD student