Final answer:
The control condition in an experiment serves as a comparison for evaluating the effect of the treatment.
Step-by-step explanation:
The condition of an experiment that contrasts with the experimental condition and serves as a comparison for evaluating the effect of the treatment is the control condition. The control condition is important because it allows the researcher to determine if any changes observed in the experimental condition are truly due to the treatment being tested or if they are due to other factors.