Final answer:
The group in a randomized experiment that receives no treatment is called the control group. It's used as a benchmark to compare against the treatment group and often receives a placebo to eliminate bias through random assignment and blinding methods.
Step-by-step explanation:
In the context of a randomized experiment, the group that receives no treatment is referred to as the control group. This control group plays a crucial role by serving as a benchmark, allowing researchers to compare results against the group receiving the actual treatment, known as the experimental group. During the experiment, participants in the control group might receive a placebo, which is a "fake" treatment designed to have no effect, ensuring that any outcomes can be attributed to the actual treatment under study rather than psychological effects or other forms of bias. Random assignment is a key process used to allocate participants to the control or treatment groups, ensuring that each participant has an equal chance of being in either group and minimizing the influence of lurking variables.
For example, in Jonas Salk's polio vaccine experiment, the control group received a saline solution instead of the actual vaccine. The inclusion of a placebo helps researchers maintain a double-blind approach, where neither the participants nor the researchers know who is in the experimental or control groups, which helps control for the placebo effect and other biases.