Aug 25

Cause and Effect Analysis

The purpose of a Cause-and-Effect analysis is to identify the cause(s), factor(s), or source(s) of variation that may lead to a specific event, result, or defect in a product and/or process. The Ishikawa diagrams (aka Fishbone Diagrams or Cause-and-Effect diagrams) is simply a tool to be used along with Brainstorming and the 5 Whys. These diagrams provides a structured way to help you think through all possible causes of a problem which in-turn assists in carrying out a thorough analysis of a situation.

Cause And Effect Diagram Figure: Cause and Effect Diagram

How to start?

Step 1: Identify the problem
Document the problem you face in detail (eg – who is involved, what the problem is, and when and where it occurs). Remember: be specific. From the “Fish bone” analogy perspective, outcome of step # 1 can be thought of as the head and spine of a fish. From the “Cause-and-Effect” analogy perspective, this is considered as the effect

Step 2: Identify categories
Identify all the factors that have a potential or may contribute to the problem. Personally, I note down all factors irrespective whether they contribute or not as it helps me validate it again during my brainstorming sessions. In other words, feel free to have as many possible factors as possible and don’t restrict yourself. Then categorise these factors into logical segments / blocks. There are recommended categories for the Manufacturing & Service industry. It is not necessary to restrict yourself to those, so feel free to maximise / leverage categories that suit your business. Typical common categories that I’ve encountered across different industries are as follows:

  • Machine (Technology / Systems)
  • Process
  • Products & Services
  • Policies & Rules
  • Place
  • Material (raw material, consumables etc.)
  • People (Can be further categorised into internal, competitors, suppliers & customers – as appropriate)
  • Management
  • Skills
  • Money
  • Surroundings (Environment)

The categories resulting out of step # 2 can be thought of as the bones of a fish / primary causes that could lead directly to the effect. I hope my explanation is alluding the reason why this piece of analysis technique is also called as “Fish Bone” / “Cause and Effect”

Step 3: Brainstorm possible causes
For each of the categories that have been selected in step # 2, brainstorm possible causes that may contribute to the problem for each of the categories, one by one. The causes resulting out of step # 3 can be thought of as the smaller bones of a fish / secondary causes that could lead directly to the primary cause.

Step 4: Perform detailed analysis – Ask Why?
For each of the smaller bones – i.e. causes of problems within each category, reason “Why” multiple times to each cause & answer sequence until you come up with possible root causes. Depending on the complexity and importance of the problem, you may want to investigate the most likely causes further by carrying out surveys, setting up investigations, carrying out process measurements, etc. These may assist you in validating your work thus far and perhaps also answer few of the “Whys”. I tend to agree when fellow professionals recommend asking the question “Why” at least five times even to the silliest of causes. Whilst it may sound silly, but the result could prove in a vital information for the exercise sought for.

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