The PRMIA website says “Just over 50% of those who have sought the PRM designation have been successful. Individual exams have pass rates that are between 50% (Exams I and III) and 75% (Exam IV).”. I am not surprised, I and III are the hardest. If you have done any maths beyond high school, and you have handled it OK, II should be easier than I or III. I’m guessing, from what the website says, that the pass rate on II is between 50% and 75%.
Jim