Randomization
For each trial, an IT manager generated a random assignment sequence using a block of 10; the list was not disclosed to the investigators. Allocation concealment was ensured using a computerized random assignment system. Randomization was programmed and piloted. Participants who did not complete the survey were replaced by other participants, whereas the intervention and control arms were ensured to be well balanced across vignettes. When the required sample size of the first trial was reached (i.e. 300 participants), subsequent participants were enrolled in the second trial.