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A scientific control augments integrity in experiments by isolating variables as dictated by the scientific method in order to make a conclusion about such variables. In a controlled experiment, two virtually identical experiments are conducted, but the factor being tested is varied in only one of them. This serves to further isolate any causal phenomena. For example, in testing a drug, it is important to carefully test that the supposed effect of the drug is produced only by the drug itself. Doctors achieve this with a double-blind study in a clinical trial: two virtually identical groups of patients are compared, one of which receives the drug and one of which receives a placebo. Neither the patients nor the doctor know which group receives the real drug, which serves both to curb researchers' bias and isolates the effects of the drug.

The scientific control is used as a constant to show the effect a given environment has on certain variables.

Negative control
A control sample where a negative result is expected, to help correlate a positive result with the variable being tested. Example: a measurement of background radiation when trying to test the effects of a certain substance on local radiation levels.
Positive control
A control sample that is known to produce a positive result if the test is working as expected. Example: printing a test page on a printer with its own driver software to test that it has been installed correctly, before testing the printing behaviour of another piece of software.