Experiments are done by many people with different rules and guidelines.  Some experiments are done through methods that may not yield very accurate results. In the scientific community, experiments are done with  controls for the purpose of having a basis for comparison when it comes to the interpretation of results.  If there are no controls, then a particular experiment wouldn’t be fairly judged whether it achieved its purpose or not.  Other details of the experiment also wouldn’t be supported by a factual basis if there are no controls.

Whether the experiment is done in school by elementary students or by skilled scientists, the use of controls is essential and very important in showing how a particular thing or condition should behave or change under normal conditions.  This supposed normal condition is given by the control specimen or group, and without it no comparison can be drawn from the said experiment.

In the case of experimenting with the growth of a particular plant species, for example, a typical control specimen would involve the specific plant species to be exposed to normal conditions like enough sunlight and watering for a given day.  Other specimens meanwhile may have additional details such as added nutrients to the soil for one sample and less sunlight exposure for the other sample.  With the control group in place, one could then draw out comparisons for the other two samples which are important in trying to make a generalization or conclusion in the said experiment.  The other samples would then be compared to the control sample if the specific plant species is able to grow taller in the sample with soil nutrients or in the sample exposed to less sunlight.

The control sample may also be used as a basis for the color of the plant.  The other samples may then be analyzed if their leaves have much brighter or duller colors when compared with the plant in the control sample. So with this basic example, the control served as the basis for comparison in the experiment.  This also applies to other experiments using other samples and conditions.