Which statement best describes random assignment in clinical trials?

Which statement best describes random assignment in clinical trials?

• A. Subjects were randomly assigned to the groups.
• B. Allocation concealment is about concealing the randomization sequence from those enrolling participants.
• C. Allocation concealment is about concealing the group labels after assignment.
• D. Allocation concealment guarantees identical baseline characteristics.

Answer: (A)

Random assignment means using a random mechanism to place participants into different study groups, with the goal of balancing known and unknown factors that could affect outcomes and reducing bias that can occur during enrollment. The statement that subjects were randomly assigned to the groups describes that exact process—randomly allocating participants to groups. Allocation concealment, while related, is a separate safeguard. It prevents those enrolling participants from knowing in advance which group the next participant will be assigned to, so they cannot influence enrollment based on that knowledge. The idea that group labels are concealed after assignment is not the purpose of allocation concealment, and it does not describe how randomization is performed. Also, even with proper randomization, baseline characteristics are not guaranteed to be identical; randomization reduces imbalance but does not guarantee it.

Random assignment means using a random mechanism to place participants into different study groups, with the goal of balancing known and unknown factors that could affect outcomes and reducing bias that can occur during enrollment.

The statement that subjects were randomly assigned to the groups describes that exact process—randomly allocating participants to groups.

Allocation concealment, while related, is a separate safeguard. It prevents those enrolling participants from knowing in advance which group the next participant will be assigned to, so they cannot influence enrollment based on that knowledge. The idea that group labels are concealed after assignment is not the purpose of allocation concealment, and it does not describe how randomization is performed. Also, even with proper randomization, baseline characteristics are not guaranteed to be identical; randomization reduces imbalance but does not guarantee it.