Difficulty level of a question refers to the ratio of incorrect to number of times asked. Suppose a question is asked 6 times and the number of times answered correctly is 2, the difficulty level of a question is 67%.
We can further analyzed from the incorrect answers the most common wrong answers was given 4 times, that shows us the most common doubt/myth about the question asked and as a tutor we would save on the future occurrence of a situation by giving more details on the concept of the question and clear the common doubt.
This analysis helps us(tutors) project the chances of question being answered correctly if asked. As a smart paper setter always decide on the demography of the successful candidates based on the setting of paper.
Looking in to the difficulty level of the questions in the bank we can easily decide on the combination of questions in order to get the desired number of successful candidates and also clearly filter out the cream.
This makes the paper setting as per our wish less difficult!