Exit Polls can be just as inaccurate as regular polls

[mr_lebowski]

7. Agree on all counts ...

And the reason that exit polls were considered the best available poll is that you're polling people who actually voted, not just people who either said they were (or were otherwise determined to be) 'likely'. You remove the variable of 'enthusiasm' as well as possible biases like 'people who say they're voting GOP are inherently more likely to follow thru with casting a ballot'.

A lot of issues arise when trying to apply statistical principles to things that are not, in some sense, a hard/physical measurement ... rings of trees, heights of 10 year old boys, etc. When you deal in hard data, and you sample randomly in a significant enough way, you'll never be 'wrong', it's not mathematically possible.

But with polling ... there's difficulties with true randomness, as well as with enthusiasm, lies (a particular problem if only one 'side' is apt to lie), people changing their minds, etc. These can be adjusted for, according to certain known principles, but it'll never be quite the same as measuring hard values.

And readers/people interpreting polls need to understand that. It becomes a lot more common to see a population where the value is out on the outer edge of the sample's confidence interval, esp. if you only use 95% instead of 99%.