National Pass Rates for Mechanical PE exam
The National Pass rates for the mechanical PE exam will fluctuate from test to test. However, the average pass rate of all people taking the exam will generally be around 50%. This includes both first time and repeat takers.
The difference between the first time test takers and repeat test takers is dramatic. NCEES lists first time test takers passing the test at ~76% while repeat test takers only passed the exam at ~37%. Everyone has their own theory as to why the repeat test takers have a harder time passing the exam.
My opinion as to why repeat test takers have a harder time passing is based upon nerves and preparation. People taking the exam for the second time will be going into the exam with a slight chink in their armor. Their egos have been bruised after failing the first time and they might have a harder time focusing on the exam. Another thing which I think effects the repeat test takers is preparation. Unfortunately repeat test takers often don't try to change any of their study habits going into the second exam. They rely on the same methods they used for the first time. Typically this involves working more practice problems...and that's it. They don't take the time to really evaluate their weaknesses and knowledge depth. Don't make this mistake. Focus on what you need to learn and then go do the work. You can look at my eBook Mechanical PE exam Strategies for some guidance, but the main thing you have to do is evaluate your situation and focus on what work needs to be done.
Here is a link to NCEES showing you the most up to date pass results: TEST RESULTS