Final answer:
Rats that are administered 20 ng/g BPA are in the treatment group in an experiment, as this group receives the substance being tested. The control group would receive no treatment or a placebo, allowing for a comparison of effects due to the BPA treatment.
Step-by-step explanation:
In an experimental context, rats administered 20 ng/g BPA would belong to the treatment group rather than the control group. In studies that involve chemical substances such as BPA (Bisphenol A), the control group is typically given no treatment or a neutral substance such as saline solution, whereas the treatment group receives the substance being tested, which in this case is BPA.
For example, a control group might receive a vehicle that does not include the active compound, ensuring that any observed outcomes can be attributed to the BPA treatment the experimental group receives. In many experiments, the control group will receive a placebo to protect against bias caused by expectancy.
The independent variable in this scenario would be the presence or absence of BPA, while the dependent variable might be various physiological or behavioral responses observed in the rats as a result of the treatment.