5Why vs. 8D - Problem Solving

adisc

Starting to get Involved
Hello All,

I would like to ask about root-cause analysis in 8D reports, namely if we have in D4 sections: root-cause for occurence & root-cause for non-detection and also to the 8D template is attached tab with 5Why to fulfill, and for instance this 5Why is resolved in full 5 steps --> which step should be put in the 8D template as a root-cause for occurence / non - detection? The first one or the last one?

Hope for your reply.

Thanks!
 

AMIT BALLAL

Super Moderator
Final cause (Answer after asking last why) is the root cause. And root cause for both occurrence and non-detection has to be addressed in 8D and necessary actions have to be taken to eliminate both of these root causes (Corrective action).
IATF16949 additionally asks to identify root cause related to system as well (If your organization is IATF16949 certified / seeking certification).
 

adisc

Starting to get Involved
Final cause (Answer after asking last why) is the root cause. And root cause for both occurrence and non-detection has to be addressed in 8D and necessary actions have to be taken to eliminate both of these root causes (Corrective action).
IATF16949 additionally asks to identify root cause related to system as well (If your organization is IATF16949 certified / seeking certification).

Thank you very much for the quick reply.

Additionally, could you please explain me more relation between Ishikawa and 5Why? I mean, that Ishikawa help out to find potential root-cause in different areas, when we decide to pick this one, then we put it to the 5Why analysis? And this concerns to both occurence & non-detection?
 

AMIT BALLAL

Super Moderator
Thank you very much for the quick reply.

Additionally, could you please explain me more relation between Ishikawa and 5Why? I mean, that Ishikawa help out to find potential root-cause in different areas, when we decide to pick this one, then we put it to the 5Why analysis? And this concerns to both occurence & non-detection?

Correct. Ishikawa diagram is to be used to identify potential causes that might have occurred causing occurrence / non-detection of the nonconformity.
After Ishikawa analysis, the causes identified have to be validated by checking whether it really occurred. After validating causes, use why-why analysis further for the validated causes - to find out the root cause(s).

Use Ishikawa and Why-why analysis to find out root cause related to occurrence and non-detection both.
 

Miner

Forum Moderator
Leader
Admin
Just to clarify:
  • Ishikawa diagram is a structured brainstorming tool used to identify potential causes for further investigation. That is, it is pre-work to the investigation.
  • 5 Why is used to document actual causes that have been confirmed by objective evidence to be true. The most common mistake made with 5 Why is when the creators sit around a table (or at a computer) and add what they consider the most likely causal chain without going on the floor and collecting evidence. The 5 Why is a documentation of the "crime scene investigation", not a brainstorming tool.
 

Randy

Super Moderator
Wanna point the finger at someone? Use 5-Why

Wanna point the finger at the process? - Use 8D
 

Jim Wynne

Leader
Admin
Just to clarify:


5 Why is used to document actual causes that have been confirmed by objective evidence to be true. The most common mistake made with 5 Why is when the creators sit around a table (or at a computer) and add what they consider the most likely causal chain without going on the floor and collecting evidence. The 5 Why is a documentation of the "crime scene investigation", not a brainstorming tool.
5-Why is a way of avoiding superficial "solutions," nothing more. It assumes that the person or people performing the root cause analysis lack basic reasoning skills or even the knowledge of what "root cause" means.

There are times when a cause may be correctly inferred by examining a discrepant part. The challenge is to not stop at something like "dull tool" and consider why the tool was allowed to deteriorate before something bad happened. In this sense, there's no reason that the exercise shouldn't be part of a brainstorming effort.
 

optomist1

A Sea of Statistics
Super Moderator
Ishikawa...5 Whys are typically used in support of or are tools with which one executes an 8D. Unfortunately in real life all these tools are under utilized...it takes time and discipline to execute a meaningful and useful 8D root cause>>CA. The drive to RC>>CA quickly takes its toll on getting to the real RC
 

Mike S.

Happy to be Alive
Trusted Information Resource
Wanna point the finger at someone? Use 5-Why

Wanna point the finger at the process? - Use 8D

Strongly disagree. I use 5 why's quite often and very, very rarely does it point to a person as the root cause.

Any tool, including 8D, can be (and often is) misused. Just this week I got an 8D that was pathetic. Is that the fault of the tool or the user?
 

Kiran Walimbe

Involved In Discussions
Normally the 5 Why technique leads to a ‘single’ dominant root cause, which serves the purpose if the organization is in a hurry. Or when the problem solvers are junior employees not well versed in scientific methods. However, as Dorian Shinin recommends, one needs to find and eliminate at least three root causes, which he calls as Red X, Pink X and Pale Pink X, in order to solve the issue near completely. That could be only be done thru’ methods like Ishikawa Diagram; applied to Occurrence as well as to Detection. So, best is to use both the methods preferably supported by Kepner Tregoe method to isolate the real causes.
 
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