The Mirror, the i and lots of local papers are today all running stories about their "big Brexit survey" which purports to show a majority of people want to remain in the single market. (1/...)

It claims relevance due to the unusual large sample size - 200,000+. As you'll hopefully know, a big sample size alone does not make a poll accurate or meaningful. What determines whether a poll is worth paying attention to or not is whether it is *representative* of the public

The classic illustration of this is the Literary Digest poll - a magazine that used to do polls of literally millions of Americans at Presidential elections, and got it catastrophically wrong in 1936 when George Gallup's representative poll got it right.