what is a negative control

A negative control is a group of individuals or cases that is treated in the same way as the experimental group, but that is not exposed to the experimental treatment or factor. Negative controls are used in experiments to reproduce a condition that cannot involve the hypothesized causal mechanism but is very likely to involve the same variables as the experimental group. Negative controls are included in the experiment to reduce variables and ensure that experimental results are valid. Results from the experimental group and negative control group can be compared, and any difference in outcome is caused by the presence of the experimental treatment in the experimental group. In contrast, a positive control group is a control group that is not exposed to the experimental treatment but is exposed to some other treatment that is known to produce the expected effect. Positive controls are particularly useful for validating the experimental procedure.