Let's assume; you need to score at least an average of 55 points over 2 tests to pass for an exam. It was decided that no matter how bad you did, to applaud you even took the effort to sit down and take the exam your lowest possible score is always 10 points. Now you did your first test brilliantly (score of 100 points!), so you can say that for the second test even in the 'worst-case scenario' - in which you only get 10 points - you would still pass. In this case (of which there are more you can think of) there is a clear limit to how negative the scenario can be. For me, in a case like this you would not have to take into account that you might be run over by a bus on the way to the exam or that the school goes up in flames so you are not even in the opportunity to take the exam!