A survey of Plato, that is, the man who created the discipline.
That is because, for Plato, to be a philosopher meant to be one who had turned one's soul (periagoge) away from the merely phenomenal world of shadows on the cave wall, and had climbed up into the light of the truth of the forms, especially the truth that, at the "height" of the journey, one sees that the form of the good, the form of justice, the form of beauty, and the form of truth all come together as one. That one, of course, we call God, as did Plato. To have failed to make that turning of the soul was to be stuck in the world of shadows, about which there was opinion (doxa), but no true knowledge (episteme). Thus, thus who lectured and taught without having made the turning were lovers of opinion (philodoxos), or sophists, and not philosophers. Plato explicitly said the main defining characteristic of the philodoxer was the denial of the One, i.e., atheism. So philosophy was defined, by its founder, as the rejection of and fight against atheism.
Therefore, when they do these surveys and ask how philosophers if they are atheists, and soon as they check 'yes' they should be dropped from the survey.