Polling is very new to me and I have a naive question:
Looking HuffPost Pollster, I am trying to understand how are numbers like "Clinton: 49%, Trump: 37%" obtained.
First of all, in every poll a number of questions (typically 7 to 20) are asked. There are two cases:
1) direct question: one of the questions is simply "If the general election were held today, and the candidates were [...], for whom would you vote?" Like Bloomberg, NBC, etc, then the numbers are just the answer of this particular question and have nothing to do with remaining ones.
2) indirect question: For example in this poll by Morning Consult, there are 11 questions and none of them directly asks whom to vote for. Of course question like "Do you approve or disapprove of the job Barack Obama" is strongly correlated, but I have no idea how numbers like "Hillary Clinton (D) 42% Donald Trump (R) 37%" are obtained from these 11 questions.
So my question is simply the following:
a) In the first case, why beat around the bush and ask ten other questions? Isn't it a waste of time/money?
b) In the second case, do they build some magic statistical model to predict the chance of winning based on the answers to various questions and never tell you how to do it?