Controlled Variable
A controlled variable is one which the scientist holds constant (controls) during an experiment. Thus, we also know the controlled variable as a constant variable or sometimes as a “control” only.
However, the control variable is not part of an experiment, but it is important because it can have an effect on the results. Remember that it is not the same thing as a control group.
Any given experiment will have numerous control variables. It’s important for a scientist to try to hold all the variables constant except for the independent variable.
If a control variable changes during the experiment, it may invalidate the correlation between the dependent and independent variables. Whenever it is possible, control variables should be identified, measured, and recorded.
Examples of Controlled Variables
Temperature is a much common type of controlled variable. Because if the temperature is held constant during an experiment, it is controlled. Some other examples of controlled variables could be the amount of light or constant humidity or duration of an experiment etc.
Importance of the Control Variables
Although control variables may not be measured as they are not recorded, yet they can have a significant effect on the outcome of an experiment.
Therefore, the lack of awareness of control variables may lead to faulty results or what is called “confounding variables”. So, recording control variables makes it easier to reproduce an experiment and to establish the relationship between the independent and dependent variables.
For example, suppose we are trying to determine whether a particular fertilizer has an effect on plant growth. Here, the independent variable is the presence or absence of the fertilizer, whereas the dependent variable is the height of the plant or rate of growth.
If we don’t control the amount of light, for example, we perform some part of the experiment in the summer and some part during the winter, we may skew our results.
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