I posted this similar question before but I didn't really clarify the values properly.
I'm trying to figure out a way to calculate the SD from these below:
Mean Pre-operation Glucose 1 = 12.2, SD =13.5
Mean Post-operation Glucose 2 = 9, SD =8.7 N= 11 people enrolled in surgery
% reduction in mean glucose = ??, SD = ??
I know calculating % reduction is easy to calculate, but how do I calculate SD?