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This article is about how to use five Why analysis methods to do fault review, the editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

Recently, a R & D student participated in the fault review and sent his analysis to me on double check. I found that some of the causes of the failure did not go too deep and stayed on the surface, resulting in subsequent actions that may address the symptoms rather than the root of the problem. This phenomenon is actually quite common, and we can try to use a simple and effective root cause analysis (RCA:root cause analysis) method to do a better fault review: 5 Why analysis (5 whys).

Methodology

Overview of the method [1]:

Whys is a repetitive interrogation technique used to explore the causality behind a particular question. The main goal of the technology is by repeating the question "Why?" To determine the root cause of the defect or question, each answer forms the basis of the next question. The "5" in the name comes from an anecdotal observation of the number of iterations required to solve the problem.

Main ideas of fault review of five why methods

Lengthen the logical chain to find the underlying cause

Abandon subjective assumptions and logical traps

Distinguish between phenomena and causes

Step by step analysis, do not jump to a conclusion directly

The reason never lies in the individual, do not take such as "human negligence", "lack of attention" as the root cause

5 main steps of why method

Decompose the problem and find the phenomenon [2]

Ask 5 why (note that 5 here is an approximate number, which can be less than 5 or greater than 5) until you can no longer ask why to find the root cause.

Ask the question from the final answer to see whether the logical chain is established in reverse and verify it.

Practice

Give a few examples of how to use it. Here is an example of a classic case and a historical online failure review case that I was involved in (the review did not use 5 why analyses, so we can see the difference).

Classic case

Phenomenon: the east outer wall of a museum has very serious corrosion and needs to be refreshed frequently.

Simple analysis and measures: after investigation, you found that the museum cleaners used a highly corrosive detergent when washing the walls, which led to the corrosion of the walls. So the follow-up measure is to require cleaners to change to low-corrosion detergents when cleaning the walls next time after repairing the walls by spray brushing.

5 Why analyses and measures:

The first why: why does this cleaner use highly corrosive detergents?

A: because there is often a lot of bird dung sticking to the east wall, it can't be cleaned with ordinary detergent.

The second why: why is there so much bird droppings on the east wall?

A: because there are many spiders on the wall, and these birds feed on spiders, they often move around the wall.

The third why: why are there so many spiders on the wall?

A: because there are a lot of bugs on the wall, and spiders feed on them

Fourth why: why are there so many bugs on the wall?

A: because there are several windows on the east wall, the light in the museum will pass through here at night, and these phototaxis are attracted by the light.

So the solution is to install thick shading curtains at the windows and close the curtains before sunset every day.

Well, we seem to have the root cause and the solution, and we deduce it the other way around:

When the thick curtains are closed, the insects with strong phototaxis will not be attracted.

Phototactic bugs no longer gather, spiders no longer gather [logical]

Spiders no longer gather, and spider-eating birds no longer come often to move [logical]

The spider-eating birds are no longer active, and there is no longer much bird droppings on the east wall [logical]

There is no longer much bird droppings on the east wall, and cleaners do not need to use highly corrosive detergents [logical]

Does not apply highly corrosive detergents, walls are no longer always corroded [logical]

At this point, we are sure that we have the root cause and the right solution.

Fault review case

Phenomenon: merchants use bank transfer serial number to query bills and find that transaction records are missing.

Simple analysis and measures: (did not use the conclusion of 5 why analysis before) because get (0) only got part of the data, so R & D redo the full get (0) analysis of the code.

5 Why analyses and measures:

The first why: why use the serial number to query if the transaction record is missing?

A: because customers expect to be able to use this serial number to query multiple (days) billing information

Second why: why are there multiple (days) billing information for the same serial number?

A: because the bank is closed on Saturday and Sunday, the Friday, Saturday and Sunday bills will be transferred together to generate the same serial number, which is related to multiple (day) billing information.

The third why: why does the system not return multiple billing information associated with a serial number?

Answer: because the get (0) method is used in the code, only the first item of data is taken

The fourth why: why is the get (0) method used in the code?

A: because the get (0) method is not prohibited / reminded in coding, the R & D does not pay attention to the risk in the development.

So the solution is to promote get (0) risk at the R & D architecture level, use clear business semantics to define code processing replacement get (0), and remind get (0) in the code scanning tool that it is high-risk coding.

In turn, it is deduced and verified:

The R & D architecture level understands the risk of get (0), and is reminded of high-risk coding when the code is submitted. Research and development will be careful to use get (0) or avoid using get (0) [logical]

All research and development use get (0) cautiously. If you choose to continue using get (0), then the tooltip risk [logical] in the code for submitting the query bill.

After the tooltip get (0) risk, when designing the code, the R & D pays attention to whether there are one-to-many scenarios in the business scenario [logical]

There are one-to-many scenarios in which R & D pays attention to business scenarios, and to a certain extent, it is more likely to analyze and perceive the bank merger payment scenarios [logical]

The reverse deduction logic chain is correct, the solution is established, and the solution is not attributed to human processing, but to architectural governance and tools. The previous solution only focused on the risk of get (0) in the code at that time, and did not track it continuously, so it only addressed the symptoms rather than the root of the problem.

The above is how to use 5 Why analysis to do fault review, the editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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