Methods of Experimental Control 

Essential questions 

What means of control can be exerted in experimental settings to achieve non-biased results?

How to create and test a null hypothesis?

Physical control of the experiment provides for the equal exposure of all subjects to the independent variable. This is achieved through the careful application of treatments of choice to the experimental group(s) while controlling all conditions of the experiment.

In setting up the experiment, it is important to remember the importance of the experimental and control group being probabilistically equivalent. That is that the makeup of the two groups and their response to the same treatment should be as close as possible. The probabilistic equivalency is determined by statistical methods that take into consideration the variability of traits within each group, as well as the size of each group. The larger the size of a study group is, the smaller is impact of individual trait variabilities onto the outcome.

Once the experimental and control groups have been established, a researcher treats them the same way, except for the independent variable treatment of the experimental group that the researcher is applying to study its outcomes. 

Physical control also includes the control of all experimental conditions that can affect the independent variable.

Selective control involves indirect manipulations that select in or out variables that cannot be controlled in the experimental conditions.

Statistical control is applied to the variables that cannot be controlled by physical or selective manipulation. 

Findings of the experimental research are reproducible under the same experimental conditions. This provides the opportunity for the data to be independently verified by other researchers and helps minimize the subjectivity in the analysis and interpretation. 

Experimental method provides the foundation for testing hypothesis and objective analysis of the problem. Initial experiments investigate the reasoning behind the null hypothesis that offers no statistical difference between the experimental and control groups and has no explanation or predictive power for the phenomenon in question. Better-defined hypotheses are followed by the experiments, data collection and analysis. The experimental outcomes can confirm, refute, or define the accuracy of the hypotheses.

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Suggested readings

Page P. (2012). Research designs in sports physical therapy. International journal of sports physical therapy, 7(5), 482-92.