I suspect that most of the times numbers are used in the media, people are being misinformed in some way. Frequently it’s by ignoring the margin of error. I’m going to discuss this with others on this afternoon’s Global Christian Perspectives. I’m providing a couple of links:
Polling Fundamentals: Total Survey Error – explanation of the various elements that might cause a poll to be off.
Margin of Error (Langer Research) – Allows you to calculate the margin of error for a poll provided you have the data.
Why the Polls Missed Bernie Sanders’ Michigan Upset – Important in explaining in some detail what elements of various polls were off in this particular case.
Bottom line, however, is that a poll is not the election, i.e., it shows what people think when it is taken, not at the time of the election. It doesn’t predict; prediction is the result of analyzing the data.