Positive control

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One says that positive control has been achieved when what happens is what was intended to happen and that's all that happens. The Columbia accident demonstrated that NASA had not achieved positive control of the Shuttle Program.

Positive controls demonstrate whether your manipulation of the variable produced the expected effect. Eg.: You are provided with a sample dissolved in water (i.e. your “unknown”), and want to know the level of saccharides present. The Benedict’s test (a reagent added to a sample) is designed to show a colour change in the presence of saccharides. Your test sample: the unknown sample, with Benedict’s reagent. Your positive control: a known amount of saccharide (or a range of several samples of known amounts of saccharide), with Benedict’s reagent. The colour of your unknown sample can be compared to the positive control sample(s) to estimate the amount of saccharide in your unknown.

This article refers to positive controls in experimental science. In air traffic control, positive control is the practice of controlling aircraft whose positions are determined by direct radar observation.

A positive control is a reactant that certainly causes an effect when applied to a cluster of test organisms.

The positive control in experiments reveals that a certain procedure works according to expectations and actually gives you the expected results. It elucidates that the experiment is functioning as it should; in general practice this means that your subject(s) are exposed to a substance that is known to have a certain effect.

Contrast this with the negative (or standard control) where you expose your subject (or experiment) to a substance or condition that is known to have no effect.

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