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Re: Five Whys

by Ratazong (Monsignor)
on Oct 29, 2018 at 13:40 UTC ( #1224838=note: print w/replies, xml ) Need Help??


in reply to Five Whys

Thanks for your research, eyepopslikeamosquito! I like the way you structure your nodes, giving a good overview, and citing relevant literature for deeper understanding. Great work!

I have some experience with 5why, also for software. I think it helps to force teams to think about the ways they develop (software), especially about the interfaces between them. This "side effect" alone gives big benefits (especially because the root-cause is likely related to interfaces).

Regarding the method itself, I have some doubts: too much depends on how exactly you answer the "why" question. Minor differences in wording lead to different directions of the next "why"-question. And thus you might arrive to a totally different root cause.

The inherent assumption of the method ("there is only one (relevant) root cause") is IMHO quite questionable. In my experience, there are often multiple reasons that "come together". Of course you can tackle this by applying 5why to various bones of your Ishikawa-diagram ...

Summary: In my eyes 5why is a valuable tool, but mainly because of the side-effect of triggering discussions and understanding, not because of its simple theory of finding a root cause by asking five questions.

Rata

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Re^2: Five Whys
by cavac (Curate) on Oct 29, 2018 at 16:29 UTC

    Regarding the method itself, I have some doubts: too much depends on how exactly you answer the "why" question. Minor differences in wording lead to different directions of the next "why"-question. And thus you might arrive to a totally different root cause.

    Agree. I have seen (and even participated) in this process. More often than not, this turns into "ok let's find some questions and answers for this paperwork so we can get back to real work". 5W is certainly a good tool to start training your team to do deeper investigations, but it is by no means a full solution for backtracking issues.

    The inherent assumption of the method ("there is only one (relevant) root cause") is IMHO quite questionable. In my experience, there are often multiple reasons that "come together". Of course you can tackle this by applying 5why to various bones of your Ishikawa-diagram...

    But the fishbone also gives the impression that each of the different root causes don't interact with each other until the end, if i understand that one correctly.

    Reality is often times much more messy, with some issues slowly making each others worse over time while others are new and only come into play at the very very end, or have lingered harmlessly for years or decades until the circumstances changed. Circular reasoning and things interacting (or not interacting) in unexpected ways under unexpected circumstances can also play a role.

    And a single long standing root cause can split into multiple pathways of issues that only turn into the final failure when they meet again.

    perl -e 'use MIME::Base64; print decode_base64("4pmsIE5ldmVyIGdvbm5hIGdpdmUgeW91IHVwCiAgTmV2ZXIgZ29ubmEgbGV0IHlvdSBkb3duLi4uIOKZqwo=");'

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