Do you believe in ghosts?

So my family (my mom, brother and perhaps father) believe that maybe they have a ghost living in their house. What do you think? My mom found dirt on the floor of the house a couple of weeks ago and she was the last to leave and the first to come home. (They called everyone with a key and no one had come over.)
Then a couple of nights ago my mom was in the bathtub and heard the dryer turn off. Then she heard the door to the dryer slam shut and then turn back on, so she went downstairs to ask my brother about it. He said he thought it was my mom and vice versa. So my brother loaded his gun (yes, I know a very dumb idea, we have talked about it and he won't do it again) and they went looking through the house (my mom yelling "come out, we have a gun" lol) . They didn't find anything downstairs so they went upstairs looking. When they were upstairs they heard a crash downstairs, so they woke my dad up. They didn't find anything but no one slept well that night. The next day, my mom's day off, she went to my sisters because she didn't want to be home alone. They ruled out the possibility of a racoon or squirrel because there are no droppings in the house and squirrels or raccoons don't turn dryers on and off.
Then on Sunday night when they came home a cup of pens and pencils was turned over in the kitchen and the clock on the bathroom wall was knocked off onto the floor.
Practical joke or ghost? What do you think?