During a clinical trial, which procedures should the investigator follow?

• A. The sponsor's marketing plan
• B. The trial's randomisation procedures
• C. The participants' personal preferences
• D. The site equipment maintenance schedule

Answer: (B)

In a clinical trial, investigators must follow the protocol’s predefined procedures, including how participants are randomized. Adhering to the trial’s randomisation procedures ensures allocation is unbiased, maintains allocation concealment, and preserves the integrity of the comparison between treatment groups. The investigator’s duty is to implement the randomization exactly as specified, document assignments, and not alter the process. The sponsor’s marketing plan is outside the conduct of the trial, participants’ personal preferences cannot override the protocol, and while a site equipment maintenance schedule is important for safety and data quality, it is not the set of trial procedures that governs how participants are randomized or treated.