I have a test containing questions with 3 levels of difficulty:
+------------+------------+-------+
| Question | Difficulty | Score |
+------------+------------+-------+
| Question 1 | 1 | 100% |
+------------+------------+-------+
| Question 2 | 1 | 100% |
+------------+------------+-------+
| Question 3 | 2 | 25% |
+------------+------------+-------+
| Question 4 | 2 | 75% |
+------------+------------+-------+
| Question 5 | 3 | 25% |
+------------+------------+-------+
| Question 6 | 3 | 0% |
+------------+------------+-------+
Difficulty could mean something like
- Beginner
- Normal
- Expert
The average of the scores is ~54%, but this does not seem fair, because the candidate only answered the easy questions well.
What is the best formula to calculate the final score to reflect the knowledge level of the candidate for 3 difficulty levels? Can we extend this formula to n difficulty levels? What is the method used in education?