A Christmas nativity scene is seen on display at Jose Luis Mayo's workshop on December 16, 2014 in Madrid, Spain. (Photo by Pablo Blazquez Dominguez/Getty Images)

Reading polls isn't easy. The data can only be so accurate, and it can often be tempting to draw too broad of conclusions.

Witness this new poll.

Surveys tend to break down religious groups by Protestants, Evangelicals, Catholics, Muslims, Jews, etc. People who don't fit into any of those categories are labeled "unaffiliated."

Data from Pew shows about 16 percent of Americans fit into this category. And to the layperson, "unaffiliated" might appear to be simply atheists and agnostics.

But look at this (other) Pew survey on Christmas. It asked people whether they believe in various aspects of the Christmas story in the Bible. And among unaffiliated Americans, fully 30 percent say the Baby Jesus was born to a virgin, and 53 percent -- a majority! -- say he was laid in a manger.

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For people who don't appear to be religious, a lot of them seem to believe what's written in the Bible.

A few folks on Twitter noticed the numbers.

But, in reality, unaffiliateds aren't just atheists and agnostics. In fact, most of them aren't. Just 4 percent of Americans fit into either of those two categories, per Pew's numbers. The other 12 percent of unaffiliateds are split between "secular unaffiliated" and "religious unaffiliated" -- about 6 percent each.

So about three in every eight religiously unaffiliated Americans say they are still religious. But 53 percent say they believe in Baby Jesus in the manger. Hmmm.