Do You Believe In Ghost?

Actually at first I dont believe that there is really a ghost or if you will die your soul will remain on earth because before, I thought it doesnt exist. This belief was changed when I witnessed an unbelievable experience. This is based on my experience.

When I was in grade 6 my classmate who was sitting beside me already informed me not to sit on the vacant chair infront of her. She said  that  her grandmother who just passed away was sitting in there. After she said that to me I got confused on what she meant because I saw nothing but an empty chair infront of her.