Is it a rule to fill in all the 5 why in order to get the actual root cause?

P

Priss80

#1
In problem solving methodology, 5-why analysis there are 5 step to drill into root cause. May i know is it a rule to fill in all the 5 why in order to get the actual root cause? I discovered that some of the root cause can get at 3th why.
 
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John Broomfield

Staff member
Super Moderator
#2
Priss80,

No, the number of times your cross-functional problem solving team asks why may be more or less than 5.

The number of whys depends on how big a step is made to link an effect to possible causes.

John
 

somashekar

Staff member
Super Moderator
#3
In problem solving methodology, 5-why analysis there are 5 step to drill into root cause. May i know is it a rule to fill in all the 5 why in order to get the actual root cause? I discovered that some of the root cause can get at 3th why.
It is generally believed that by the 5th 'Why' you will hit the rootcause. It could also be the 6th in some case. Nothing hard and fast on the number of why's....
If you have discovered the rootcause by the 3rd why, so be it. However are you sure there are really no further exploration opportunities in your system.... no further why question really ??
 

Mike S.

Happy to be Alive
Trusted Information Resource
#4
As you have seen, there is no magic in the number 5.

After all, "roots" themselves vary in size, location, and depth. If you take RCA to the extreme you go back to God or the big bang or whatever, but that is not helpful.

If you find a "root" cause that you can control and you believe will eliminate the problem, and keep a sharp eye out for contributing causes that might need a fix as well, give it a go and see what happens. PDCA.
 

Steve Prevette

Deming Disciple
Staff member
Super Moderator
#5
I would suggest that 5 is a rule of thumb established from experience. Generally, folks who stop before getting to 5 are less likely to have pulled the string far enough to find the "real" cause(s), and will only end up trying to fix symptoms.
 

Mike S.

Happy to be Alive
Trusted Information Resource
#6
There is also too often a difference in theoretical best case RCCA scenarios and what you are able to actually accomplish in the real-world.

Practicality means you will often be forced to stop and execute a CA one or two whys short of what you may be sure is the ?true? (or closer to ?true?) root cause because you know going to the next step or two will result in having to turn around and go back to something further from ideal but which you and/or your team have some control over. Finding a ?true? root cause over which you will not be able to exercise any control is only of academic value, not practical value.

Politics is one of the frequent reasons for this, IMO. For example, if experience tells you that the company President will not let you fix the problem at the 5th why, you might as well stop at the 4th if you have control over that and work with what you have, not what you wish you had. JMHO.
 
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