The Domino Theory
If you'd like to catch up:
When I was a little girl, I enjoyed playing with dominoes. I never wanted to play the actual game; no, I wanted to stand the dominoes upright in elaborate patterns so that I could knock 'em down in a line. I found this domino effect to be most entertaining, despite the fact that I really wasn't very successful in my attempts to create the most complex, beautiful domino pattern ever.
Given my appreciation for dominoes, it's not surprising that I discovered Bob Nelms early in my study of RCA. Bob uses the Domino Theory of root cause to explain how a failure or error occurs. The Domino Theory states that every failure is in fact a series of failures that play upon each other: a physical cause that's triggered by a human cause, which is in turn fed by a latent cause.
However, I'm not content using Bob's theory as is; when I develop training, I do whatever I can to develop mnemonic devices to facilitate data transfer from short-term memory to long-term memory. For example: remember the characteristics of a root cause that I defined in Part I? A root cause:
- can be fixed.
- explains the failure or event.
- can be identified with a reasonable amount of effort.
- is controlled by management.
- is specific.
Well, I've turned those criteria into the acronym "FERCS." FERCS is a great way to remember the characteristics of root cause; for one thing, it's not an actual word, but it sounds vaguely as though it might be an obscenity. This makes it good for a laugh in training - and what people find funny, they remember.
Likewise, I've tweaked the Domino effect that Nelms describes; I call it the PHaTS Domino Theory (I'll give you three guesses what song I play during training workshops when we get to the PHaTS Domino Theory). In essence, the PHaTS Domino Theory renames one component - purely for the purposes of designing the acronym, you understand:
- Physical cause: this is the physical failure that led to the event. For example, let's say that the bad event is a car wreck. The physical cause might be that your brakes failed. It's important to know that this particular domino may not be present in every business problem per se. For example, with the bug in the order entry software I described yesterday, there's no true physical failure, although I would consider the software failure to be akin to the physical cause.
- Human cause: Nelms states that every physical failure is triggered by a human failure or cause. In the example of the software, the human cause might be that the programmer failed to account for international shipments. In the case of the brake failure, there are several possible human causes: perhaps the the technician who last worked on your brakes did a shoddy job; perhaps the brakes have been squealing for the last six months and you've put off getting the brakes done; perhaps the brakes were defective in the first place, but the quality control personnel at the manufacturer didn't catch the defect.
and..
- Top Secret cause: This is the latent cause that Nelms describes. At its most basic, Top Secret cause represents the 400-lb. gorilla that everyone pretends isn't there. Top Secret causes are those unspoken rules or policies that everyone follows even though those rules are not publicly defined. They are the assumptions and beliefs that drive business-as-usual for your business.
In RCA for business problems, it's usually not too difficult to isolate the physical and human causes; the top secret cause(s), however, are a different story. In order to identify the top secret cause, you need the cooperation of the people involved in the problem/failure, because you have to find out what they were thinking (remember, this is about learning rather than blaming, and there's an enormous difference between, "Why did you decide to do it that way?" and "Why on earth did you do that?). Management, too, may be somewhat wary of the notion of top secret cause, because when you identify those assumptions, beliefs and unspoken rules, you turn a big old mirror on the management team - and on the subtle (and in some cases not-so-subtle) messages that they're sending to the organization.
By the way, if you're interested in Bob Nelms (and his take on human nature as the real root cause of all failure is fascinating), I recommend his book, What You Can Learn From Things that Go Wrong.
Tomorrow: Step One of conducting RCA.
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