What you need to know about polling

Leighton Walter Kille follows up on the Trump upset with a review of the basics of polling — explaining why, for example, a poll's sample size is related to its sampling error, and why even the best pollsters sometimes come up wildly wrong: "It’s important to remember that polls are a snapshot of opinion at a point in time. Despite 60 years of experience since Truman defied the polls and defeated Dewey in the 1948 presidential election, pollsters can still miss big."