N-of-1 trials might be designed for a single person, but they still follow some of the basic principles of a large RCT. For instance, N-of-1 trials randomly assign participants to different treatments or interventions to test the effectiveness of each one. This randomization helps control for other factors that might affect the results of the study.
In the trial, participants are asked to try the treatment for some days and, on other days, to try either a different treatment or their usual routine. When they do the treatment or not is based on random assignment, like flipping a coin.\