Simply: are questions that companies ask at interviews copyrighted or
are they public domain? Can they be collected/resold?

They are copyright.

I'm appliying for a copyright on the following questions, so do not use them:

*Who was your previous employer?
*Where did you go to/attend college/university/school?
*Where do you see yourself in five years?
*What is your name?
*Please fill out this application.
*How many fingers am I holding up?

:-)

What about more specific questions?

The relevant tests are:

1. Have the questions been "fixed in a tangible medium of expression"?
If I say something to you it is not copyrighted. If I write it down or
tape it, it can be.
2. Is the question or questions original? This is a tricky one, but
the bar is quite low (much lower, for example, than patents). So, for
example,  the "facts" in a telephone directory cannot be copyrighted.
I suspect that you can't copyright something short and obvious, like
"How old are you?" but a series of non-copyrightable questions could
acquire copyright protection if you presented them in the same order.
(Thus, no word in the English language can be copyrighted, but you can
copyright how those words are strung together into a poem.)
3. Are you copying the idea or the expression? This is also tricky.
Certainly, you can't hold copyright on an idea like "asking an
interviewer about the duties of their last job," but you could hold
copyright on the exact words used to express that question. Justice
Hand wrote about "patterns of generality" that allow someone to write
a play about a "vain and foppish steward who became amorous of his
mistress" without violating William Shakespeare's Twelfth Night
copyright. (Which has, of course, expired.)
4. Is it fair use? There are a couple types of fair use. You can get
around a lot if you're writing a parody, for instance. Important to
you is the "substantiality" of the work. You can always quote a
portion of a work, particularly if you comment on it. So, if you're
writing a book about how companies misuse questions, you can give
examples and critique them.

Note that copyright is inherent in the act of creation. It does not
require formal filing or even notice. So, don't listen to people when
they say it's not copyright unless it has a © symbol and is on file at
the Library of Congress. This used to be true. It is no longer.

Lastly, you should consider if there are any NON-copyright problems,
eg., patents, trademarks, trade secrets, contracts or things that
would fall under unfair competition laws. A company could argue that
the question-sheet was not supposed to leave the office, or that
confidentiality was an unstated condition of the interview.

Lastly lastly, you should factor in how likely someone is to bring
suit, and what the result of that would be. A company that feels
cheated may well bring suit against you even if they don't have a very
good case. Mostly, however, fighting suits in costly for both sides.
Mostly, companies will ask you to stop/remove/etc. the copyright
infringement. Getting *damages* for copyright infringement is pretty
difficult.

Check out Edward Samuel's _The Illustrated Story of Copyright_ for an
accessibile introduction to copyright law.

Lastly, a caveat: this is not legal advice. It may (and probably does)
contain wrong information. For legal advice, consult a lawyer, not
some guy on the internet momentarily pretending to be one. Pay your
lawyer more than $4; it's the law. :)

Rereading your question, it seems likely to me that you are thinking
of oral questions. As stated, the questions need to fixed in a
tangible medium. Oral communication is not copyrighted by anyone,
unless it is written down or taped. If someone reads something off a
sheet, obviously it can be copyrighted.

With oral communication, there are other laws in force. Most states
prohibit you from taping someone without their knowledge. Do it over a
phone interview and you could well hit some federal wire charge--I
have no idea what the law is.