What is a Controlled Experiment?

Definition: A controlled experiment is a test performed where all elements remain equal except the variable that is being studied. It is an experiment where all other conditions except the one that is being researched is kept exactly the same.

What Does a Controlled Experiment Mean?

These experiments are normally part of a regular procedure to test a given hypothesis. Hypothesis are assumptions, they are statements that must be tested to either be proven or disproven. They normally contain a certain variable that is the one being tested, these are called independent variables. In order to prove the hypothesis the independent variable is tested under the same conditions to evaluate the results and therefore, to evaluate the hypothesis’ accuracy.

The dependent variable is the subject that is being exposed to the independent one, and the hypothesis will be proven if the dependent variable behaves as expected or it will be disproved if it doesn’t. Controlled experiments often include experimental groups and control groups, the first one beings the ones exposed to the independent variable and the second ones being the ones that are not exposed to it, and took as a baseline to compare results. Each group must be controlled, this means that both have to be subject to the same environmental conditions in order to guarantee the experiment’s accuracy and reliability.


A coffee shop is currently testing its coffee making techniques and they want to do it through a controlled experiment. In order to do so, they put 5oz. of coffee in five different filters and will add water heated at five different temperatures and then taste the coffee to see which one tastes the best. In this case, the coffee will be the dependent variable and since each experiment will be made with 5oz. of it, the conditions are properly controlled.

The hypothesis being tested is “Coffee filtered with water heated at 100°C tastes better than coffee filtered with water heated at other temperatures”. Also, the filters and the environment is the same for each sample. The control group will be coffee filtered with water heated at 100°C. The other four temperatures tested are 50°C, 70°C, 90°C and 120°C. After the experiment was performed, coffee experts decided that the one filtered with water heated at 90°C was the best one. The hypothesis in this case was disproved.