I’m not so sure the 40/60/80 is that reliable. Some people would have got zero for not finishing parts of the am and this calculation would give them a 40 when infact they scored nil. I guess is cuts both ways with the mid and higher range scores though.
angoff method is just getting CFA charterholders to sit down and say whether they think the average CFA charterholder would get it right. http://www.altalang.com/beyond-words/2008/10/06/what-is-the-angoff-method/
past exams may not be the right benchmark, since this years exam questions were “perceived” to be easier…