But, not so powerful that they are immune to human error. Few things are.
Analogously, this is one reason why our school teachers strongly encouraged proofreading (clearly, something that I do not do too effectively at Gemba Tales).
You know, critically reading what you just wrote to ensure that it is clear, well-organized, flows logically, without misspelled words…so that no one thinks you’re a total idiot.
Well, the same type of proofreading reasoning applies to problem-solving.
Two tools come to mind. One is 5 Whys and the other cause-effect diagrams (a.k.a. fishbone diagrams or Ishikawa diagrams).
Many folks are familiar with Taiichi Ohno’s “famous” 5 why example. It can be found on page 17 of his classic book, Toyota Production System: Beyond Large-Scale Production, published by Productivity Press.
In response to a downed machine –
- Q: Why did the machine stop? A: There was an overload and the fuse blew.
- Q: Why was there an overload? A: The bearing was not sufficiently lubricated.
- Q: Why was it not lubricated sufficiently? A: The lubrication pump was not pumping sufficiently?
- Q: Why was it not pumping sufficiently? A: The shaft was worn and rattling.
- Q: Why was the shaft worn out? A: There was no strainer attached and metal scrap got in.
[I must admit, to me it seems like Mr. Ohno’s example should have reflected 6 whys. The fifth answer would have been metal scraps wore the shaft down. The sixth why would have queried why metals scraps ended up contacting the shaft, with an answer pointing to the missing strainer. But, who am I?]
So, how can you check the 5 Why analysis for soundness?
Read it backwards, with the word “therefore” or “so” between each response. For example (and pardon the run-on sentence), the strainer was missing, therefore metal scraps contacted the shaft, therefore, the shaft wore out, therefore, the pump did not pump sufficiently, therefore…you get the point.
This simple practice will help the problem-solvers identify if they are perhaps missing something and/or if their “train” of causal relationships does not make sense somewhere. The practitioner needs to sufficiently understand the root cause(s) in order to identify effective countermeasures.
Consider it 5 Why proofreading.
Fishbone diagrams require a logic check as well. The diagram is an effective means of organizing and displaying theories of potential root causes.
Often the diagram has a number of primary, secondary and tertiary “bones” leading into the “head.” The bones represent (potential) causes and the head represents the effect.
Because the diagram can have a lot visually going on, it makes sense to proofread it – not just at the end of the diagramming, but as it is being constructed as well. This will reinforce the cause and effect discipline of the folks creating the fishbone.
One effective way to proof is to read the diagram from most minor bone(s) to more major bone(s), all the way to the head – for each causal “thread.” Just like the 5 why example above, you can throw the word “therefore” or “so” in between to make sure that it makes sense.
An example, the driver was inattentive, therefore he was tired, therefore, he had the accident. Oops, looks like the most minor bone (secondary bone) and the major bone (primary) are reversed.
(Yes, inattentiveness is probably a major bone, with fatigue, texting, and eating as discrete secondary causes.)
Fishbone diagrams “tell” a story of potential causes. Reading them aloud helps people to hear the story and then see it among the many bones (sometimes a challenge for the newly indoctrinated) and is an excellent way to make sure the causal relationships make sense.
So, while I didn’t quite appreciate my 5th grade English teacher, Ms. Cahill’s request to more rigorously proofread my own work, I can appreciate it within a lean context. I hope that you do as well.