Control Group
A control group is a set of experimental units that receive no treatment (or a standard/placebo treatment) and serves as the reference point for comparison. The control group allows isolation of the treatment effect by comparing the treatment group outcome to the control group outcome.
Real World
In the NHS's trial of a new migraine drug, one group received the actual medication while the control group received an identical-looking sugar pill, allowing doctors to measure improvement beyond what a placebo alone would produce.
Exam Focus
State that the control group provides a baseline for comparison — answers must explain why it is needed, not just that it exists.
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