One reason for using random assignment in psychological research is:

• A. To guarantee that the results will always support the researcher's hypothesis.
• B. To make sure that only the most qualified participants are selected for the study.
• C. To increase the likelihood that participants will behave in socially desirable ways.
• D. To ensure that each participant has an equal chance of being placed in any experimental group, reducing potential bias.

Answer: (D)

Verified step by step guidance

1. Understand the purpose of random assignment in psychological research, which is to distribute participants across different groups in a way that minimizes bias.
2. Recognize that random assignment helps ensure that each participant has an equal chance of being placed in any experimental group, which balances out individual differences.
3. Know that this process reduces the likelihood that pre-existing differences among participants will affect the outcome, increasing the internal validity of the study.
4. Distinguish random assignment from other concepts like random sampling, which relates to how participants are selected from the population.
5. Conclude that random assignment is not about guaranteeing results or selecting qualified participants, but about creating comparable groups to fairly test the hypothesis.