I think "quiz" type of questions are pretty ineffective at filtering out candidates. You do filter out the bad candidates, but great ones could also be left behind. Who knows, the person could be an brilliant developer who got nervous during the interview and had a blank. Or the phone call is breaking up. Or the person is in a non-ideal location. Etc... I would not filter out a potential hire just because the person couldn't remember the SQL syntax on the spot...

For me, a senior developer is someone who is able to work in a TEAM, be dependable (i.e.: The guy who you can call at the 3am with an urgent matter), mentor others and be able to contribute and implement new processes and practices. The technical stuff is important but should not be the main filter IMO.

It also seems to me that you want to apply a certain logic or algorithm to the process. Personally I prefer to call up and just have a conversation with the person (trying to find out the aspects I listed above). Unless I am Google and I am getting a gazillion applications, that's different...