Question

imagine you are collaborating with researchers studying the effect of marijuana on driving. participants are assigned by chance to either a) receive a pill that contains thc, the active ingredient in marijuana, or b) a harmless placebo pill. neither the researchers nor the participants know who is getting which pill. after taking the pill, participants are asked to drive a computerized driving simulator. the number of collisions participants have is measured. researchers determine which pill participants get by using: a single - blind procedure. a double - blind procedure. random assignment. nonrandom assignment.

Explanation:

• Random assignment is the process of randomly assigning participants to different groups in a study, which matches the description of "assigned by chance" here.
• Single-blind only keeps participants unaware, double-blind keeps both participants and researchers unaware of group assignments (which is present here but the question asks how they determine group assignment, not the blinding procedure).
• Nonrandom assignment is the opposite of chance-based assignment, so it is incorrect.

Answer:

random assignment.