Rubbish (unfortunately) (Score 1)

The scenarios sketched in the post are not exactly close to the real world. Multiple choice tests no matter how hard can easily be constructed so there probability of passing the exam simply by guessing is insignificant. For example:

There are 20 questions and you have to be correct on at least 16 of them. If there are just two options on each question your chances of passing by guessing is 1:170 if there are four options your chances are 1:2600000.

If you are interested see http://en.wikipedia.org/wiki/Binomial_distribution