control group

American  

[kuhn-trohl groop] / kənˈtroʊl ˌgrup /

noun

1. (in an experiment or clinical trial) a group of subjects closely resembling the treatment group in many demographic variables but not receiving the active medication or factor under study and thereby serving as a comparison group when treatment results are evaluated.

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control group British  

noun

1. any group used as a control in a statistical experiment, esp a group of patients who receive either a placebo or a standard drug during an investigation of the effects of another drug on other patients

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Etymology

Origin of control group

First recorded in 1950–55

Compare meaning

How does control-group compare to similar and commonly confused words? Explore the most common comparisons:

• control group vs. experimental group

Example Sentences

After three weeks, the participants who knowingly took placebo pills experienced lower stress levels than both the deceptive placebo group and the control group.

From Science Daily • Jun. 25, 2026

A three-year study showed it slowed progression by 75% compared to an external control group.

From The Wall Street Journal • Jun. 19, 2026

The company is leaning toward a trial that compares patients receiving the therapy against a control group receiving standard treatments and a “sham” procedure to rule out any placebo effect.

From Barron's • Jun. 17, 2026

Yet Dr. Makary’s deputy Vinay Prasad overruled them and rejected the drug because the trial lacked a control group.

From The Wall Street Journal • May 29, 2026

According to him, a majority of the cancer victims who’d been prayed for were out whooping it up on the town, while their counterparts in the control group had shriveled up and died.

From "Anthem of a Reluctant Prophet" by Joanne Proulx