Dr. Sullivan is conducting a clinical trial to determine if vitamin XX can improve test performance of students in an introductory college nutrition course. Dr. Sullivan puts all the students' names in a hat and draws names to determine if they will be placed in the control or the experimental group. The experimental group receives a capsule of vitamin XX and the control group a "sugar pill" that tastes and looks identical to the vitamin XX capsule. Neither Dr. Sullivan nor the participants know who is receiving which treatment. This experiment is BEST described as