- So let's talk about variation. So what I mean by variation is that
you make a measurement and the data is not identical.

- And that can happen both within an experiment that the individual
cell lines or animals or people on which we collect data are all a
little bit different from each other. There's also variation between
experiments if the exact same observations were made on different
days, with different equipment, or by different scientists, we will
frequently see variation due to that replication. When I say variation
or noise, I'm referring to the same thing. What I mean is the fact
that when you make a measurement on one occasion, or on one sample
versus another, even if in truth, things are the same, the
measurements might be a little bit different. And that can be for
biological or for technical reasons.

- So noise can arise either from the biology itself or the physical
world. It could also arise from your experimental technique or your
measurement. If the noise is arising from the biological system
itself, that can be very interesting. It gives you great insight into
many biological processes. In fact, many people analyze noise arising
from gene expression, for example, as providing information about how
gene regulation works. So noise can provide information. On the other
hand, noise can arise from your equipment, or your technique, or the
way you're going through your entire experiment. And obviously, that
kind of noise is in a way, confounding your results because it's
adding more variation that can be difficult to interpret.