The control variable is the thing you keep the same and is everything that is not the independent variable. The Control Setup is there for the sake of comparison.
In an experiment, you want to manipulate one variable only. That way, you will be able to draw a conclusion about how differences in that one variable affect whatever system or organism you're...
Two kinds of controls: Positive and Negative.
Depending on the test/Instrument, Positive controls will have an indication or contain the specific substance that the test or instrument is used for....