When there are parts of an experiment that scientists cannot carefully control, they should
A. change their hypothesis to include all the variables.
B. ignore the other variables and record only the important data.
C. redesign the experiment to be sure they are testing only one variable.
D. try to set up a new experiment that tests a few variables at once.

Question

When there are parts of an experiment that scientists cannot carefully control, they should
	A.	change their hypothesis to include all the variables.
	B.	ignore the other variables and record only the important data.
	C.	redesign the experiment to be sure they are testing only one variable.
	D.	try to set up a new experiment that tests a few variables at once.

anonymous · Answer

To me the correct answer is C. Even if you don't manage to properly define all the variables, you can trace the changes that occur during the experiments and express those as a constant. Then you can adapt the experiments, or perhaps change them, to eventually acquire a complete definition of all the variables. Science history is full of such examples: at first some experiment managed to describe a certain phenomenon in large terms, leaving behind some constants which have been given a better explanation only with further studies. 

Think of the difference between the macroscopical and the microscopical gas laws.