ok, so I now know the independent and dependent variables for my experiment, however, do I need a control? If I had one, would it be the hair out of a live rat? Or does my project not require one? Im not sure.
That's a great question! Let's take a moment to think about what a "control" is. A control is something that does not undergo the treatment. In your case, the "treatment" is death, followed by natural decay. Your idea of pulling hairs from a live rat is a great idea!
Just make sure that you take the necessary precautions (so you don't get bitten), and that this is something you can do without permits. (As researchers, we have to get permits to work with live vertebrate animals, especially if we might cause them even momentary pain.)
Here are a few things you should keep in mind:
1) You will want to measure more than a single hair at each time point, since not every hair will begin at the same size. This includes your control hairs (from the live rat).
2) You actually have two potential controls:
a) Hairs from a live rat (no death).
b) Hairs at the time of death, if possible. This would establish a baseline value for you. However, since it's not likely that you will be able to pull hairs at the exact time of death, your live rat hairs can serve as your baseline.
3) It would be helpful if you can ask the lab or facility from which you obtain your rat(s) to note the exact time(s) of death for you.
You're doing great!