∞ generated and posted on 2016.08.21 ∞
Experimental conditions for which expected change in the dependent variable is assured so long as the experiment is working properly.
A positive control is an experimentally effected change in the dependent variable that is achieved especially through manipulation in some manner of the or an independent variable, i.e., a purposeful change in experimental conditions that has the effect of showing the researcher what a positive result at least could look like.
Positive controls are a necessary component of experiments particularly if experimental results are negative since then, without a positive control, one would have no idea whether the experimental protocol or equipment could possibly have given rise to a positive result.
A positive control, in other words, is what you perform in order to be sure that a positive experimental result at least could have occurred.