In experimental design, what is the primary function of randomization?

• A. It assigns participants to groups with known causes
• B. It ensures identical individuals across groups
• C. It is not related to extraneous variables
• D. It helps balance extraneous variables across groups

Answer: (D)

Randomization assigns participants to conditions by chance, which helps balance extraneous variables across groups. This balance reduces systematic differences that could bias outcomes, making it more likely that observed effects are due to the intervention rather than preexisting differences. It does not guarantee identical individuals across groups, nor does it rely on assigning people to groups based on known causes. It directly addresses extraneous variables by distributing them evenly, helping to isolate the treatment effect.