In a scientific experiment, what is the control variable for?

Please help, i don't really get what it's for! Thanx in advance


xxxIn a scientific experiment, what is the control variable for?
the control is used so that you have something to compare the results of your experiment to. The control is unchanged throughout the experiment.In a scientific experiment, what is the control variable for?
The control is for two things.





One, it will confirm that the experiment works as it should (e.g. in a bacterial experiment, a control can confirm sterility of the growth media).





Also, a control will give you the ';zero response'; if you use it for a calibration, in which case it is also known as a blank.
There are 3 variables which can be identified:


-manipulated variable: factors which are changed during experiment


-responding variable: factors that change according to changes in manipulated variable


-fixed variable: factors which does not change at all during experiment





In a scientific investigation, one variable is manipulated to study its relationship with a responding variable.
control variables establish baselines. There are expected statistical results from the status quo %26amp; they should be accounted for prior to altering the test poulation.