truck I learnt very early on that probability maths is best left to those that understand it. And I am 100% certain that I don't and its not obvious to me anyway some of the solutions. BUt I did learn that they are right.
That equation does look familiar. But thats from over 20 years ago now 1st year Eng maths.
The 25% guess factor on a question is correct but the combinations of probabilitys gets a bit confusing (to me anyway) when looking at the final proberbility.
The way the Question banks have been designed with 2 stupid answers and 2 similar but one slightly wrong. Sometimes all of them wrong but you have to choose the most correct. Means that you cant really apply the "standard" maths to it all. Most questions are a 50/50 choice with two discarded as stupid.
If anyone with even the sightest bit of proffessional examination setting got there hands on the questions I am pretty sure that the whole set of exams would be deemed flawed.
Unfortaunately now it is possible to hammer the QB's and get through with very little conceptual understanding of the subject matter and even get on paper very good results.
Its certainly not uncommon on the line to use terms like dirty side of the drag curve and "once you have trimmed for the speed" to be met with complete confusion from the pilot. Who had passed there ATPL theory under 12 months previously with a 98% average.