Yeah, that is why a lot of Agricultural/Biosystem engineers sit for the Civil or Mechanical exams (especially the second time around).
OK... I wrote the first thing that came to my mind, which just happened to start with an "a"... how about we look at some of the latest data:
Examination, First-time takers, Repeat takers
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PE Architectural, 66%, 26%
PE Chemical, 81%, 27%
PE Civil, 67%, 34%
PE Electrical and Computer, 66%, 27%
PE Environmental, 73%, 35%
PE Mechanical, 64%, 30%
PE Naval Architecture/Marine, 89%, 100%
PE Structural I, 38%, 25%
PE Structural II, 51%, 37%
PE Agricultural, 75%, 44%
PE Control Systems, 80%, 49%
PE Fire Protection, 42%, 34%
PE Industrial, 69%, 40%
PE Metallurgical, 55%, 54%
PE Mining and Mineral, 84%, 35%
PE Nuclear, 80%, 80%
PE Petroleum, 93%, 33%
Can we agree that maybe there's a correlation between exam discipline and difficulty? Can we agree structural and petroleum or naval architecture/marine are on opposite ends of the pass-rate spectrum? Does someone want to look at a larger data set?
Or would you have me believe that, on average, people who take the structural exam are just not as smart as the average naval architecture/marine engineer?
Please don't misunderstand me... I'm just trying to suggest that some disciplines are harder than others. And states that designate as "Professional Engineer" make it difficult to assess capabilities. Still, with a good argument, I'm sure I can be convinced I'm wrong.