The part of the experiment that is not being tested and is used for comparison of the experimental results is the control.
The control is the standard against which the researcher compares the results from each treatment group (level) in the experiment (ex. amount of water, temperature).
For example, if you wanted to study the effect of fertilizer on grass growth, the obvious control would be the section of lawn with no fertilizer.
A control group should be used when conducting an experiment. This group receives the same attention as the test groups, however, it will not be influenced by the variable the other groups are testing.
The following parts of an experiment should be included in most science projects and should be identified in the written paper:
1. The independent variable is the variable that is intentionally changed in the experiment, such as the temperature of the water in which an effervescent tablet was dissolved.
2. The levels of the independent variable are the different values of the independent variable, such as using water at 10°, 20°, 30°, 40°, and 50° C. The levels of the independent variable can also be thought of as the experimental groups that are set up.
3. The dependent variable is the variable that responds to the changes in the independent variable. For example, the time it takes for the tablets to dissolve in the different temperatures of water is the dependent variable.
4. The control is the standard against which the researcher compares the results from each treatment group (level) in the experiment.
5. The repeated trials are the number of times the experiment is repeated to determine how the independent variable affected the results.
6. Constants are the things that are kept the same each time one of the trials in the experiment is repeated.