By the way your story on Feynman and the challenger is not completely correct. Roger Boisjoly from Morton Thiokol KNEW the o-rings were being damaged by hot gasses that escaped due to the twisting of the tang and clevis connection of the external rockets. Google it. Edward Tufte has a pretty good synopsis of it. (They didn’t use 5 whys on this. The politics was about finding root blame)
Yes, this thread has drifted way off topic. I did speak once with a person of Morton Thiokol and they stated they figured the Challenger would blow up on the pad. They were pleasantly surprised when it cleared the pad.
I was working my Master's thesis at the time using Logistic Regression. The investigation team used that tool also. and as I remember, using ONLY data available from previous launches they calculated a probability of 12% chance for "complete mission failure". The interesting thing is the Morton Thiokol engineers were never able to quantify the risk before launch. Of course, several parallels with the Columbia disaster. The "WHY's" would point you to a culture issue (aka politics).
The five why's is (are?) not perfect, but better than what I usually saw at work by senior managers, which was One Why. For example, we had a high rate of damage to government vehicles. Senior management determined that was due to people speeding, and enlisted the local sheriff's department to increase patrols. I was (after this decision) tasked to look at the data. Something like 90% of the damage occurred at less than 15 mph, and generally with the vehicle hitting a stationary object, (an obstruction or another vehicle) generally when parking or maneuvering in a parking area. That led to a whole different flow for the Why's.