What is a Controlled Experiment?

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Controlled experiment is one in which there is strict control exercised on variables, with typically one or more variables being changed or “manipulated” while all other variables are held constant or the same across experiments. This is one of the trademarks of many types of scientific inquiry. When a hypothesis is being tested, it won’t be tested as effectively if a huge number of variables are in flux. Creating an environment where the greatest numbers of variables are eliminated can help make test results more credible. An experiment with controls on variables is called a controlled experiment which usually separates research subjects into two groups such as an experimental group and a control group. The control group is practically identical to the experimental group, except the fact that the experimental group is tested on using the variable(s) while the same variable(s) values remain constant for the control group, through out the experiment.


What is expected of a Controlled experiment?

If someone wanted to examine plant response to a specific type of sound, there is potentially one way to create a controlled experiment, and multiple ways to quickly lose control. For example, the person might get 6 plants and place each one in a different area of a house. They could then expose the plants to the sound at varying times of the day. It would be easy to see haw many variables are at play. The plants are not in the same location, the sound is not being played at the same time of the day and the plants may not even be the same species.


On the other hand, to turn this into a controlled experiment, the person could do several things. He / she could make sure that plants are of the same size plant and ideally the same species. The plants could all be kept in the same location. This means that other factors like different exposure to light cannot affect the results. The same sound would have to be played at the exact same time too. Fundamentally, the goal is to make everything as similar as possible from the beginning of the test. This allows the experimenter to manipulate a single variable, the effect of the plants to the exposure to the sound. At the same time, the controlled experiment has to look at plant behavior without the exposure to the sound.


How to Setup a Controlled Experiment?

To setup a controlled science experiment, one must have a good understanding of the scientific method which is a process, a set of guidelines, used to ensure the accuracy of the experiment, thus achieving “control”. The instructions are as follows.

  • Research is essential to collect data that is used to formulate a hypothesis and to create the experiment. So, begin by doing the own research
  • Identify a problem. Without problem, there is no motive for the experiment
  • Formulate the hypothesis. Hypothesis is a statement, based on the research that is intended to provide a solution to the problem. The hypothesis is what we are trying to prove or disprove
  • Conduct a controlled experiment to prove the hypothesis
  • Identify the independent (cause) and dependent (effect) variables, and choose the variable(s) that will be modified or tested, while holding the other variables constant
  • Do not alter the hypothesis midway through the experiment. The setup of a controlled scientific experiment must be constant
  • The result may not be the one which is anticipated
  • In that case, start over again with a new hypothesis to find new variables to manipulate


What are the disadvantages of controlled experiment?

Controlled experiments can be very difficult. It is easy to overlook a variable and fail to control it. For instance, in the study of humans for a specific drug, in order to perform controlled experiments, quite a few variables needs to be managed as humans exhibit a wide variety of behavior with regard to a drug, as they come in different sizes, having different genetic markers, making the task of experimenters extremely difficult

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