Not necessarily, those that say there is not a devil, but believe that people can be possessed by a spirit are likely referring to human spirits. After all, mediums are said to be "possessed" by a spirit when they are "channeling."
While there almost certainly are people with just those beliefs, the questions in the poll were:
Do you personally believe in the existence of the Devil or not? No: 28%
Do you believe someone can be possessed by the devil or some other evil spirit? No: 28%
How often do you think people are possessed by the devil? Never: 11% (leaving 89% to answer at least "rarely")
Familiar to...