Randomization Method
Step 1: Each session is assigned to one of three treatments (“20-40”, “20-60”, or “40-60”), which is hidden from participants before the session. In order to collect 40 participants for each treatment, we assign the treatment in an ad hoc manner, but without knowing the participants’ characteristics.
Step 2: After the session starts, each participant is assigned to a quality-type (type-20, type-40, or type-60), based on their ID number during the session, randomly generated by otree. If the ID number is odd, a relatively high-quality type in the session is assigned. Otherwise, a relatively low-quality type in the session is assigned.
Payoff: During a session, otree app ("random" module in Python) secretly and randomly chooses “main part” or “risk survey” with equal probabilities, and chooses a round/question number as a payoff-relevant round/question.