[dbingham]

If the goal is to actually calculate how many words we know, then you should include an "I don't know" option. Sure, some people will choose to guess to inflate their score, but some of us will be honest because we legitimately want to know our scores.

If you force me to guess, then I'm going to guess. Not only does that give me a 25% chance of getting it right at random, but as others have pointed out, it is very hard to make a multiple choice question that isn't guessable by an astute enough test taker. I think I knew 80 - 85 of those words, but I scored 97, because those questions were very guessable.

Also, reiterating everyone else's comments with respect to the UX needing fewer clicks, and also the definitions not being exact or precise in many cases.