Polls and surveys are not infallible. Nor do they define what is true. But they do have their uses.
If they are conducted carefully and without bias, they can offer insights regarding public opinion or perceptions at a given moment in time. Among other things, polls can help us understand the mood of the moment and confirm or question trends of changing opinion.
Among the more respected polling organizations is the Pew Research Center. The center has a particular interest in measuring the role of religion in public life and how those who identify as adherents of a particular religion feel about issues and events.