What is the difference between experimenal and control setup???

Question

which one has the varialble???

Answer 1

Edited 4/20
The experimental group contains the viable being measured. The control group does not.
A prime example is the use of a placebo. When testing the reaction to something (like a stimulant) half the group is given the real pill and half (the control group) is given a placebo - a pill with nothing in it. Of course none of the test subjects know which pill they took.
The control is the way to establish a unbiased standard of comparison to which the experiment is measured. The attribute being measured is normally absent in the control. For instance, to study the "braininess" of blondes, the control group would have no blondes in it. This is another variation of the placebo.
The setup of the control is very important as an experiment can be invalidated if the control group is flawed. Some experiments can be set-up in ways to seem legitimate, but they are purposely biased to achieve a predetermined result. This is none by both the exclusion of or the addition of faulty or biased data or criteria. For example a political pollster can bias the results of his poll by including or excluding important questions or by selecting non-representative groups to "test".
Another example is the studies which were done by and for tobacco companies "proving that cigarette smoking was not a cancer threat." The scientists lied because they were paid to reach the conclusion desired. It happens more often than you would like to know and it happens in more enterprises than the science labs and courthouse steps.