I suppose it depends on what it does or says. We hear voices in my basement once in a while, the worst of which said "I'm coming to get you." I assume we have an evil spirit in our house.
How Do You Know If You Have A Evil Ghost Or Nice Ghost Living In Your House?
You get a sense by the way they make you feel when you run across their activity. It really isn't that hard to distinguish between the two, they are totally opposite. Hope this helps you out.
you might just know by felling it such as if you feel that someone is there or if you feel room tempeature in different rooms or if you see things moving hear stuff.
By its behavior. How does the ghost act? Do you feel threatened in the house? And if you are maybe the ghost isn't BAD maybe its frustrated about something.