Originally Posted by
y-oh-y
Question: Does the captain have control over the amount of Oxygen supplied to the passenger cabin?
Oxygen is not supplied to the passenger cabin (unless the O2 masks are in use). The air is just ambient air with it's normal O2 percentage (about 21%).
The air pressure in the cabin can be controlled, to a certain extent, but would normally be at the highest normal pressure for your cruise altitude that the aircraft's design (max psid) allows.