Constants and Control Groups of an Experiment

Control groups ensure that the experimental conditions aren't producing the observed reaction.

Learn about the meaning of constants and control groups in an experiment if you wish to perform a valid scientific experiment to investigate a phenomenon. Scientific experiments focus on the changing of one specific variable, the independent variable, to see how it affects the outcome, or the dependent variable. The use of control groups helps to establish what effect the experimentation alone will have on the outcome. Constants within experiments are variables which are controlled.

Control Groups: Definition

A "control group" is a group of participants, or reactants, in an experiment that has ordinary conditions. One simple example would be in a drug trial, where one group is given the new drug, and their results are compared with those of the control group, who received a sugar pill, or placebo. Likewise, if somebody was testing the effect of light on the speed of a chemical reaction, he is likely to have one control sample, which has ordinary lighting. Control groups do not have an altered independent variable.

Control Groups: Function

Control groups are vital parts of many experiments, because they show that no overlooked aspect is affecting the results. In a drug trial, the group who received the drug may improve, but it could be due to the fact that they believe they are going to get better, known as the placebo effect. To offset this, a control group is added. They are given a sugar pill, and neither group knows which they are getting. This means that if the placebo effect is influencing the results, the control group will show the same amount of improvement. If the experimental group improves even more, then the drug must be effective.

Constant: Definition

In an experiment, the constants are the variables which remain the same throughout the experiment. For example, if you are testing the effect of heat on the amount of sugar that dissolves in water, you need to keep the type of sugar and the amount of stirring constant. If you were to use a different type of sugar for one test, it may not be the independent variable, the heat, which is affecting the solubility of the sugar. Most experiments have numerous constants, the ideal being that only the independent variable changes between the experimental group and control tests.

Constant: Function

The reason for having a constant group of variables in an experiment is to ensure that only the tested variable could affect the results. For example, if you are testing the effect heavy metal music has on the speed at which you drive, the control group may be given classical music to listen to and the experimental group would be given heavy metal. If the experimental group were faster on average around a course than the control group, a positive result is to be assumed. If the constants weren't correctly managed, however, this could be an erroneous conclusion. For example, imagine that the heavy metal group were given modern sports cars and the classical group were given outdated sedans.

References

• Science Kids at Home: What is an Experiment?
• Science Buddies: Variables in Your Science Fair Project
• Science Made Simple: Science Fair Experiments