Make sure its a little yippy dog. Big mean looking dogs that don't bark are worthless. Seasoned burglars always bring a treat for dogs which will always stop big dogs. Yippy loud dogs are way more of a deterrence.
That was not the case with my first big dog. He stayed in the house, and was quiet. He would not bark when you knocked.
If you came in he would own you Not much of a deterrent, I know.
Most home robberies are local kids who know the neighborhood. They knew he was in there, and to quote one of them, " I don't like your dog, he made me pee my pants!"
I never had any trouble when he was alive. The punks got my tools about a month after he died though.