Final answer:
The experiment uses random assignment to determine whether a person is in the treatment or control group by chance, ensuring each participant has an equal chance of group assignment and maintaining the balance needed for conclusive results.
Step-by-step explanation:
When whether a person is a member of the treatment group or the control group is determined purely by chance, the experiment uses random assignment. This process ensures that all participants have an equal chance of being assigned to either group, which is crucial for achieving a balanced experimental design. This design minimizes the impact of potential lurking variables and allows the researcher to establish a cause-and-effect connection between the experimental manipulation (independent variable) and the observed outcomes (dependent variable). In such experiments, typically statistical software is used to facilitate the random assignment of participants.
To further minimize bias, the experiments often use blinding. A single-blind study prevents participants from knowing which group they belong to, while a double-blind study also keeps the researchers in the dark about the participants' group assignment. This practice is particularly important to protect against experimenter bias and the power of suggestion, ensuring the integrity of the data collected from the control and experimental groups.
In conclusion, random assignment and blinding are key components of a well-designed experiment that seeks to investigate the effects of an independent variable on a dependent variable in a rigorous and unbiased manner.