DisclaimerWhile I am a certified PMP, I can only state my opinion. This website is in no way affiliated with PMI. My disclaimer is similar to the one issued in Chapter 1 of the PMBOK. It is a "body of knowledge," a functional reference that is neither complete nor all-inclusive. PMI advocates a number methodologies that originate in a variety of vocational areas. So while these techniques may seem disparate, they are considered part of the whole body of knowledge.
The explanations herein are not a replacement for the PMBOK, PM experience, study, or testing. My goal is that my explanations here will further your comprehension of these formulas and give them greater utility.