- I read an article that said there was a primary several months ago in which pollsters took data to say that Clinton had a 99% chance of winning. Sanders ended up with a narrow victory. I guess you can't say he was wrong. Some things that are predicted to happen one percent of the time, do happen. Still probably embarrassing for those pollsters, though.
- In 1948, Harry Truman famously held up a newspaper declaring that "Dewey Defeats Truman". He didn't. Dewey had such a lock on it. As George Gallup Jr. said about this, "We quit polling a few weeks too soon." That'll do it.
- In 1936, Literary Digest conducted a survey of its readership. It picked Alf Landon over Franklin Roosevelt. It turns out that Literary Digest (which has since gone out of business for obvious reasons) mostly appealed to a higher-income type person. That skewed Republican, thus predicting a President Landon.
- In 2000 the television networks declared Al Gore the winner of Florida. That was all he needed to be president. They had to retract that, declaring the race "too close to call". Overnight the networks declared George Bush the winner. Later, back to "too close to call".
Last time we looked at how the polls work. A newscaster might say, "Candidate X is at 57% with a 3% margin of error". They usually don't mention the level of confidence. I thought they use a 90% confidence level. I saw something lately that said it is usually 95%. Regardless, they're pretty confident. But they aren't certain.
Let's take that example and use a 95% confidence level.
Candidate X is at 57% with a 3% margin of error translates to:
We are 95% sure that he is somewhere between 54% and 60%.
There is actually more to it than that. Consider a bell-shaped curve peaking at 57%. Of all the possible outcomes, 57% is most likely. Then 56%, then 55%, then 54%. Even 53% or below is not out of the question. Very unlikely, but not out of the question.
So if Candidate Y is at 45%, he/she is probably going to lose. However, it won't be because the 3% margin of error says he has to.
Pretty confusing. No wonder the pollsters get embarrassed every once in a while.
