TEENS: Only One. They simply hold the bulb and the universe revolved around them, so it magically screws itself into the socket.
IN THE CHURCH AUDITORIUM: Five, plus some observers typically.
The auditorium at my church was designed without planning for maintenance. Scissors lifts are too short to reach nearly all the bulbs. Fortunately, the fire station one block over has a ladder that Almost reaches nearly every bulb. So one of the members who happens to work at that station goes and borrows the ladder...and then the fun begins. We tie the middle or two very long ropes to the top of the ladder, which leaves four equal lengths of rope hanging off. then four men stand back and apply enough tension to hold the ladder perfectly still while sticking straight up in the air leaning against nothing. The fireman-church member climbs the ladder and changes the bulb. For the ones that he can't reach, be sits on the top rung, locks his legs in from opposite directions, then uses one of those telescoping poles with the special widget for changing light bulbs they sell. You can see how this would be worth watching.