iSixSigma

Fishbone vs. Tree

This topic contains 10 replies, has 5 voices, and was last updated by  Judy 3 years, 8 months ago.

Viewing 11 posts - 1 through 11 (of 11 total)
  • Author
    Posts
  • #55200

    Strayer
    Participant

    SS practitioners are taught to use a fishbone (Ishikawa diagram) to drill down to potential root causes. With apologies to Dr. Ishikawa I’ve never understood why this is better than a simple tree, considering that the metaphor of a spine, ribs, and bones is less clear than a trunk branching down to it’s roots. It’s harder to draw and modify even if you have special software. And it’s harder to explain to an audience. I don’t use fishbones since trees are easier and better. If I’m wrong, please enlighten me.

    0
    #199105

    JB
    Participant

    I’m generally not a fan of the fishbone. In regards to helping identify root causes – I think it’s very weak problem solving tool. When I do brainstorming, I prefer to use a cloud type / mind mapping diagram as it’s more free-flowing.

    I don’t think your wrong… The author of the book World Class Quality, Keki Bhote would also agree with you – at least based on my interpretation of his book, I think he would. But, everyone has an opinion right? :-)

    0
    #199108

    Everton da Silva Paula
    Participant

    Hello @Straydog. I don’t know if the history behind the “fishbone” is really true but when I learnt it in past, it was told me that the purpose behind the fishbone was that Mr. Ishikawa needed one thing that should be easily understood by the audience instead talking about difficult stuffs.

    This history makes sense to me……. but sometimes I do use the tool this way, I would add that anyone can recognize a good way to chase root causes using the fishbone or not.

    Hugs!!!

    Everton

    0
    #199121

    Kicab

    I don’t even use the 6M or other set of categories for the simple reason that the cause come from the process steps. So, use your tree or a flow chart or whatever. But I find simply listing the possible causes under each step is more rigorous and specific to the problem you are trying to address. It also avoids (when brainstorming) of listing wildly impossible causes.
    Be the master of the tools; don’t let the tools master you.

    0
    #199126

    Shelby Jarvis
    Participant

    This is the type of discussions I enjoy. Hopefully many people will read and challenge each other to think about how we influence processes and other people.

    I am in agreement with Kicab. I lean toward making the tool work for me and not becoming ingrained in 1 tool. I work with all functions (transactional and operational). With this, the people on my teams vary in how they learn. In this case, I am referring to the learning associated with the problem solving process. If I am with a highly innovative team, I may use one technique; if I am with a very literal team, I may use a different technique. The key is I read the team to make my best bets then adapt to the team if my first bias isn’t delivering the necessary results.

    I also use the tool as a guide. The 6M’s aren’t always applicable when working outside of operations. In these cases, I use “Failure Mode” or some other logical name for each branch/fish fin/etc.

    I feel as if it is my responsibility to have enough techniques to allow me to be flexible to reach any audience and to respect their team and personal cultures.

    0
    #199128

    Gabrielle

    I think he basically created a tool that he could name after himself, and thought it works, it can get a little messy as you build out your root causes. The Tree is much cleaner and clearer in my opinion.

    0
    #199129

    L’Orangerie Crawford

    Hello,

    I agree with Kicab. I was taught that you can identify the process steps that are the most troublesome (usually from the SIPOC) and replace the 6Ms of the Fishbone and then identify the causes for each of the steps. I found this technique to be very helpful in getting to the root cause and with my data collection.

    0
    #199130

    Chris Seider
    Participant

    The fishbone tool is great for beginning the process of improving a process. Unless data is then captured to corroborate one of the X’s identified on the fishbone, I always look skeptically at teams that said they knew the solution was …. and changed/fixed this ….

    If following the traditional L6S teaching, the fishbone is one of the first tools in the Measure phase to begin a plan to capture data to then analyze to find an X of importance to Improve the problem and then Control the system from losing the gains.

    0
    #199131

    Shelby Jarvis
    Participant

    Great point Chris. Regardless of the brainstorming technique used; the team is only identifying potential root causes. I think that is where LSS experts add value is maintaining expectations and the discipline needed to properly test and validate if/if not the issue is really the root cause.

    When I teach this topic (in the classroom or real life), I remind the team that you should expect a high failure rate of being correct in the first assumption. For example, if you circle the teams top 3 most likely potential root causes, they should expect failure from at least 2 of the 3 and sometimes all 3.

    This can result from a few reasons.
    1) The team staying at the superficial level and not digging deep enough
    2) It’s an honest wrong belief of the cause and effect.

    The key is to validate.

    0
    #199132

    Strayer
    Participant

    I’d hoped to trigger this discussion. Many of us tend to become doctrinaire about the tools we employ and teach. I think the fishbone should go into the dustbin since it’s really messy once you get beyond the ribs. What we want to do is identify potential causes. A simple tree, or even an outline, is much easier to use and much easier for the uninitiated to understand. As far as 6M’s (or however many M’s you prefer) I think these are best used as a “gut check” to make sure you’ve considered everything of relevance. If you use them as ribs or branches you tend to end up with false common causes — duplicated only because they fit more than one M. Thanks to all for your thoughts.

    0
    #199136

    Judy

    Hi all, I coach many six sigma teams and use 5M fishbone often. Before I get to ANALYZE phase, we do a pmap in MEASURE so I have that going into it. The inputs on the pmap provide a good start for potential root causes, but what if you did a bad pmap then you may miss a valuable cause. I particularly like fishbone to promote brainstorming in all M buckets, and you can drill deeper and draw sub bones on main bones with causes. I am not familiar with tree you mention. Another one is 3 legged 5 why analysis, however this one I find a challenge to teach Greenbelts. All root causes brainstormed must be supported by data or some verification. Thx good discussion, Happy New Year!

    0
Viewing 11 posts - 1 through 11 (of 11 total)

You must be logged in to reply to this topic.