Which technique helps ensure group equivalence by randomly assigning participants to conditions?

• A. Counterbalancing
• B. Randomization
• C. Standardization
• D. Matching

Answer: (B)

The key idea is creating comparable groups by giving every participant an equal chance to be in any condition. Random assignment uses chance to place participants into the experimental or control group, which tends to balance both known and unknown characteristics (like prior knowledge, motivation, or demographics) across groups as the sample size grows. That balance makes it more likely that differences in outcomes are caused by the manipulated variable rather than pre-existing differences, supporting clearer conclusions about causality.

Other techniques address different concerns. Counterbalancing deals with order effects in within-subject designs by varying the sequence of conditions for participants. Standardization focuses on keeping procedures identical for everyone to reduce procedural variability. Matching tries to create equivalent groups by pairing participants on specific characteristics, but it doesn’t guarantee equivalence across all traits the way random assignment does, especially in larger samples.