How scientific is it?
Ghosts were confirmed with quantum theory.
Ghosts are just spooky manifestations of the randomness of quantum particles.
Like, when you see a ghost move a chair, it is just that the quarks that made up the chair randomly decided to all spin to that direction at the same time, creating a net force that moved the chair to that direction.
'Ghost Busters' are actually Applied Particle Physicists who visit people's houses to calm down the quantum fields there and also study them so that maybe one day they can comprehend all the spookiness.