There are a number of reasons why someone might fail the PMP exam.

First of all, it's a difficult test. I don't care who you are, how smart you are, or how much project management experience you have. At the end of the day it's a tough test.

I have had a number of students come to our prep camps who have failed the exam prior to the course. Most of those folks considered themselves to be very knowledgeable about project management, good test takers, and quite a number of them actually held other certifications and credentials. However, when they got into the PMP exam, they soon found out that this was not a test you can logic your way through. In fact, years of experience and a dose of logic can actually be counter-productive on the PMP exam. That's not to say that there aren't those people out there who can self-study and pass... they definitely can, with the right resources.

So why do people fail?

1. Over-confident - Surprisingly, this tends to be a common problem. As mentioned above, these are the people who have years of industry experience, they have aced other certification tests, and they know their stuff. Unfortunately, it's just not the right stuff. As a result of their confidence, they tend to answer questions using their knowledge and not with the PMI-view of the problem.

2. Lack of PMBOK Guide knowledge - The majority of the PMP exam is knowledge of the PMBOK Guide. There are other concepts and information on the test, but bottom line, you must know the PMBOK and I'm not talking about memorizing 42 process names and all of their associated Inputs, Tools & Techniques, and Outputs (ITTOs).(See #3 below). You must be able to understand the processes and ITTOs conceptually. Meaning that if a problem describes a process in not-so-clear terms, you would be able to recognize that process and also know what happens before and after that process!

3. PMBOK memorization - Some folks believe that the key to success on the exam is memorizing the PMBOK Framework (yes, all 42 processes and 517 ITTOs) and I have even seen some people spend weeks on this memorization activity until they can artfully write it out on an inflated dump sheet. (There are even prep programs out there that brag about their extensive use of mnemonics and silly tricks to help you remember a huge dump sheet versus actually working on teaching the core concepts) Not surprisingly, none of them passed. While it's important to be able to recognize the names of the processes and ITTOs, memorization will not assist you in comprehending them and will actually take up precious space in your short-term memory which will be much more useful filled with conceptual understanding.

4. Test anxiety - The vast majority of adults experience some type of test anxiety. Usually, there is quite a bit riding on this exam, not the least being a tidy sum of money. Unfortunately, we are still hard-wired like our cave-man ancestors and when we are stressed we enter fight-or-flight mode. When that happens, our blood supply is actually re-routed from our brain to our large muscles... unfortunately your legs aren't going to help your reasoning or logic. Understanding the anxiety process, knowing your triggers, and using relaxation techniques can be a definite benefit in the test environment. But you also need to store the conceptual information as "learned knowledge" not in your short-term memory.

5. Difficulty with PMBOK(R) Guide concepts - Depending on a person's experience, both from an education and career perspective, the PMBOK concepts are counter-intuitive and difficult to grasp, especially if one has never seen them in practice! Other people may struggle with math and the formulas (thankfully, there are limited formula questions). A good prep program will recognize your areas of weakness and work with you on overcoming those weaknesses.

6. Reading TOO much into the questions - Most people taking the PMP exam consider themselves to be intellectuals. This is great! However, it really backfires on the exam when you read too much into the questions. The exam will tend to have questions on it that have more information than you need. You will need to pick through the details, identify the pertinent info, and answer the question. You can drive yourself crazy over-analyzing the questions.

The good news is that it's very possible to pass this exam! Hundreds of people do it every day. With a thoughtful (and humble) approach to studying and preparation, you will pass. And boy, it feels really good to walk out of that test center with the piece of paper proving it!

(As a side note, I know some very intelligent, talented project managers that were not able to pass the exam. This is absolutely no reflection on their intelligence, capabilities, or strengths. And given the choice, I would hire many of them in a heartbeat.)