It's my understanding that the definitions of these stats are as follows:
- questions = The total number of questions posted.
- answers = The total number of answers posted.
- answered = The total number of questions with at least one answer.
Remember, there can be (and often are) multiple answers on a single question. So to clarify, let's do a simple example. Let's suppose this is day 1 of the site and nothing has been posted. It would go like this:
- Starting values: questions = 0, answers = 0, answered = 0%.
- The first question is posted: questions = 1, answers = 0, answered = 0%.
- An answer is posted: questions = 1, answers = 1, answered = 100%.
- Another answer is posted: questions = 1, answers = 2, answered = 100%.
- The OP accepts one of the answers: [No change]
- A second question is posted: questions = 2, answers = 2, answered = 50%.
I believe these stats work the same on all SE sites, so if you doubt my answer I would recommend asking on meta.stackexchange.com (search first; it's probably been asked).