Supervised sessions are best run in a meeting room or another secluded place where you won't be interrupted. The only people present should be the playtester, the test facilitator, and a maximum of two observers. The observers are typically other members of the core development team—everyone should witness at least one test in order to appreciate how their game is performing on an actual player. Instruct the observers to remain quiet and make their presence as unnoticeable as possible.
If you have the capabilities, record each session! This will allow you to distribute the footage to everyone interested, and remove the necessity for observers. In the best case scenario, you’d be able to combine raw game footage ...
