When is a lot of variability too much? How precisely, quantitatively reproducible should biological signaling activation be? If you have different populations of the same cell line, treated all the same way, does it make sense if they still show about 20-40% variance in their response over the course of a bunch of replicates?
How do I know when it's us and our hands, or when it's just the fundamental variability of biology???
UPDATE: Thank gawd for sisters who understand ANOVA.