Cause and Effect Diagram...
Information | Understanding | Best Practice.
We can usually identify many problems throughout a process. The question is how best to permanently and effectively address the particular problems we wish to focus on? The Cause and Effect diagram is a method of identifying potential root causes of the problem. The first stage in the Cause and Effect process is normally the use of Brainstorming. The Brainstorming process is highly effective at extracting ideas and knowledge from participants.
Defining the problem and the scope are critical.If the problem is not clearly defined so that all involved can clearly focus on the problem, the risk will arise that suggestions will be offered during the brainstorming that do not aim to address the original problem. This can very quickly result in the team addressing the wrong problem, i.e. not addressing the real (root cause) problem.
The scope also needs to be very clearly defined up front. Too wide a scope and the process will become unworkable as there will be too many potential causes. Too narrow a scope and the problem will not be adequately addressed. Even if a problem has intuitively (say) three potential causal areas, it may be appropriate to focus on just one or two, address them, then move onto other areas. In this regard too narrow a scope, with a commitment to revisit the problem once the first set of corrective actions have been implemented may be preferable to, too wide a scope.
In a typical Cause and Effect Diagram, we identify the problem… and arrange the potential causes in a fishbone type arrangement.
If we just focus for this example on “Method”
With a focus on the Method used in the process we start to ask why.
Why would the Method cause this problem?
Why, why. why…..?
What is the effect or problem to be solved ?
If we continue asking why, we will build up the Cause and Effect diagram.
In a Cause and Effect Diagram, we need to keep asking WHY?Why could material cause the effect? (Possible answer) Poor quality batch received.
Why? Did not use preferred Vendor.
Why? The preferred Vendor could not supply in time, due to internal process difficulties.
Why ? ………….
Normally, the question “why” would go down to the fifth level, but clearly more or less levels may be appropriate depending on the complexity involved.
Once we get to the root cause, then we can consider proposing solutions to address the cause.
We continue this process for each of the spines of the Cause and Effect.The end result will be a list of potential root causes, which we can then list out, review, prioritize and implement corrective actions.
Quality Management Tools and Techniques …
- Continuous improvement utilizing Analytical Techniques.
- 5 why’s analysis
- Process Flow Diagrams/Flowcharts/Process Mapping
- Check sheets /Check Lists
- Run charts
- Scatter Diagrams/Scatter Plot
- Cause and Effect/Fishbone/Ishikawa Diagrams
- Identifying sources & causes of variation
- Control/Shewart Charts/DPU Charts
- Cpk and Ppk Analysis
- Pareto Analysis
- Bottleneck Analysis
- Etc. Etc.
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