What test or distribution should I use for before and after treatment? Say, I have 30 subjects I test their blood before and after a pill they take a pill, what kind of test should I use? I want to test mean difference, so, paired t-test? or Wilcoxon signed rank test? The data looks like this person before after #1 100 89 #2 90 75 #3 120 100 #4 132 130 ... ... ... #30 141 120 I was told use binomial with normal approximation, but don't know why. I am so confused, how should I tell? someone please help. Thanks so much.