5 why's and fishbone diagrams

#1
Hi everyone,

I'm doing a junior role in quality so I sometimes attend root cause analysis meetings, I have noticed that my company's 'problem solving form' has the 5 whys before the Fishbone diagram. The senior quality person leading the meeting, started by explaining that we should do our 5 why's first and then when the root cause is found, we insert that root cause in the Fishbone diagram, e.g. if the root cause was machine didn't have poka yoke, that we would put it in the machine category of the Fishbone. That didn't seem right to me. Is that a good practice? or is the company using the tools wrong?

My understanding was after brainstorming possible causes of a problem by using a fishbone diagram, you then use 5 why's to dig deeper.
 

qualprod

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#2
Yes it Is like You say, doing it initially, it leads you in just one direction and may have wrong results, while considering fishbone , the problem, is seen from several angles.
Hope I can help you.
 

poh.s.lim

Poh S. Lim (Minuteman Resources Pte Ltd)
#3
Hello Heiss,

Logically speaking, your approach is correct.

In my opinion, brainstorming is a technique to draw out possibilities and it can and should be used in conjunction with the fishbone diagram. Possibilities are then populated on the fishbone diagram based on the 5 or 6 'fishbones' emanating from the main backbone i.e. Man, Method, Machine, Material, Maintenance etc. Based on a discussion and analysis of the problem, the most likely cause is then isolated and then you can proceed onto the 5 Whys which will drill further down into the root cause. Of course, as you drill down, it may result in a different 'root cause' reason which may be in a different area, and so you should be prepared to drill further down that route. Hope this makes sense to you and answers your question.
 

cbearden

Involved In Discussions
#4
Doing the 5-whys FIRST sometimes help setup your fishbone with more relevant "Bones".....then you're on a more focused path to root cause.
Your Bones don't always have to be, "Man, Method, Machine, Material, Maintenance"
 

Rameshwar25

Involved In Discussions
#5
, started by explaining that we should do our 5 why's first and then when the root cause is found, we insert that root cause in the Fishbone diagram, e.
Incorrect method.
Correct method is to first arrest all possible causes through fishbone . Then Why-Why analysis with some of authenticated causes chosen from fish-bone diagram.
also consider 'Fault Tree Analalysis' to drill down root cases.
 

poh.s.lim

Poh S. Lim (Minuteman Resources Pte Ltd)
#6
Doing the 5-whys FIRST sometimes help setup your fishbone with more relevant "Bones".....then you're on a more focused path to root cause.
Your Bones don't always have to be, "Man, Method, Machine, Material, Maintenance"
I agree, Cbearden. Sometimes 5 Whys may help turn up more relevant bones.... And yes, it does not always have to be Man, Method, Machine, Material, Maintenance. That would depend on the operation / industry type, so far example a retail business could have a different set. Appreciate your correcting my post. Thanks.
 

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