Why randomly assign enrolled volunteers to drug and control groups?

• To recruit a sample that represents the wider population of patients.
• To keep participants unaware of which treatment they receive during the trial.
• To reduce differences created by choosing who receives each treatment.

What is a placebo in a drug trial?

• A matching tablet containing a smaller dose of the active drug being tested
• A treatment lookalike without the active treatment being tested
• A matching tablet containing another active drug selected to treat the condition

Tests that give a candidate drug to human volunteers are classed as preclinical research.

Participants can tell whether their pill is drug or placebo. Both groups receive the same visits. Which problem is participant blinding intended to reduce?

• Differences in starting health caused by how participants were assigned.
• Differences in symptom ratings caused by researchers knowing the treatment groups.
• Differences in reported symptoms caused by knowing which pill was received.

Patients report less pain after taking a new pill. Recovery and study care could also explain improvement. Which comparison best assesses the pill's added effect?

• Drug versus matching placebo, with assignments hidden and the same follow-up.
• Drug users' symptoms before and after treatment, with the same follow-up visits.
• Drug versus no tablets, with participants told which treatment they receive.

Participants are blinded, but a researcher who knows assignments rates their improvement. Which change targets the remaining rating bias?

• Keep treatment assignments hidden from the researcher rating improvement.
• Recruit more participants while the researcher continues to see assignments.
• Use a matching placebo while the researcher continues to see assignments.

Study R compares benefits and harms in larger controlled groups. Study S examines benefit and dose in people with the condition. Study T checks for uncommon or delayed harms during wider use after approval. Which usual stage-purpose matches fit?

• Phase 2: R; phase 3: S; monitoring after approval: T.
• Phase 2: S; phase 3: T; monitoring after approval: R.
• Phase 2: S; phase 3: R; monitoring after approval: T.

A survey links memory-pill use with higher scores. Which follow-up design most directly addresses whether the pill affects scores?

• Recruit more existing users and non-users, then compare their memory scores.
• Randomly assign eligible volunteers to pill or control, then compare scores.
• Let eligible volunteers choose pill or control, then compare their scores.