I was not able to see the questions, however, the examples given in the article were things that one would certainly expect the average Christian to know. There are a lot of different things that can influence the outcome of these kinds of surveys such as how they define the groups, how they word the questions, and how they perform the analysis. I am not sure how they defined the representatives of each of the groups but assuming that they used fairly objective criteria or based it upon peoples self-identification then this is a disturbing story.
It makes me wonder what is being discussed and taught each week in many of our churches. It is particularly important in Protestant churches that people understand the doctrines and the biblical foundations for them. There is no infallible human authority that can give the "official" interpretation of the text so each person is expected to engage with God's word directly. This survey seems to reinforce my view that we are not adequately preparing people to do this.
There is a desire on the part of teachers and preachers to be engaging and relevant and so we are tempted to avoid repeating plain teaching that we assume people know. We are often looking for new insights and powerful applications of these basic truths without necessarily adequately teaching and preaching those truths in themselves. We should never assume that people have the basics down or that if they do that they somehow do not need to hear it again. I am not advocating boring or repetitive sermons or classes but rather that the most relevant and powerful thing we can do is to always cover the foundations prior to building upon them. The neglect of foundational doctrines is dangerous because it is precisely those teachings that tie together and unify the other teachings.
Do you know and understand your church's doctrinal positions? If not, you should ask to have them clarified. If you are a teacher or a preacher, does your congregation know and understand your church's doctrinal positions? If not, why not?