What Are Constants & Controls of a Science Project Experiment?
Controls and constants are fundamental principles for scientific experiments. Scientists must identify and define them to conduct even the most basic laboratory research. While different in nature, controls and constants serve the same purpose. They reveal the impact of variables in an experiment by eliminating any factors of distortion. Students at any grade should learn these concepts before developing any science projects.
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Constants
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Constants are variables in an experiment that cannot change in relation to particular subjects or tests. For example, a scientist might test a hypothesis that apple trees which receive the most water grow the largest apples. The constants for such an experiment would include the water temperature, time of day watered, water delivery system and the age of tree. If any of these variables do not remain constant, they may account for growth differences. In order to test a variable, it must be isolated from other possible variables.
Controls
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Scientists use control groups to compare them with subjects under experimentation. Some experiments use a "no treatment" control to assess the impact of the changed variable in test subjects. In other cases, all groups receive a changed variable but the control group has a fixed one while the others get different ones. The fixed variable usually approximates the normal or typical quantity or quality in a natural environment.
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Control Group Issues
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When setting up an experiment, identify any and all constants. In theory, this is an infinite task, which explains why new discoveries continue to be made. Also consider whether the constants can be measured. Elements such as temperature and time are possible. Other factors, such as the complete DNA composition of the test subject, are not. And still others will be binary conditions. After identifying all of the variables to be fixed as constants, determine whether they all can be held at the same value during the experiment. If not, your experiment must make note of the potential impact of the variance.
Control Group Issues
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A control group must simulate real world conditions. One success factor is the size of the group. A control group that receives a placebo in a drug test must be of a large enough size to account for any statistical anomalies. Further, consider if any unexpected variables will skew the measurements of the control group. For instance, a control group that lives in a region where a nuclear accident occurred might not be helpful in testing whether a new drug reduces the likelihood of cancer. Since their chance of cancer will be raised, they will not be useful in comparing the effectiveness of the drug with test groups.
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