The Six Sigma ‘Analyze’ Phase



The Six Sigma “Analyze” phase determines the causes of defects and measures their severity. Usually this phase is broken into five analysis activities, followed by a completion activity:

Root Cause Analysis

This activity seeks the source, or root cause, of each type of defect. A convenient approach is to use “three steps” to determine the root cause: opening, narrowing and closing steps.

The “opening” step is essentially a brainstorming session. List all possible causes.

In the “narrowing” step, eliminate the causes which do not fully explain how the defects occurred.

“Close” the root cause analysis by performing further tests to validate the suspected causes of the defects. Several causes may be implicated by these tests.

Process Analysis

Each process is, in a sense, “competing” with others for efficiency and effectiveness. Do some business competitors excel in a process comparable to the one under study? What is the theoretic limit on the process, and how far is it falling short?
 
Create a detailed process map to determine where defects may be introduced, or where efficiencies may be found.

This activity differs from the root cause analysis because its focus is on “movement”: where do requests or materials go? The root cause analysis is more likely to find problems in the inputs or the equipment.

Data Analysis

Data analysis often begins by using a standard statistical analysis tool, such as Minitab.

Question even the validity of the data that has been collected. Was there a bias in the sampling?

For example…and this should have been addressed in the Data Planning activity…all the project data may have been collected during a weekday shift. Night or weekend shifts may have completely different employees, and their defect patterns may be quite different. Was data collected just before or just after a routine maintenance task?

This is also the time to check whether there are surprising statistical patterns in the data. While even random numbers will show some patterns when subjected to enough analysis, it should be clear from this phase whether further data collection is required.

Resource Analysis

This usually addresses problems in efficiency and timeliness. If inputs are not available on time, then production will lag. Are there too few forklifts? Is the supplier late with deliveries; if so, why?

Some production and process defects will be caused by inadequate human resourcing or training. Fatigue may be a factor to be considered, and may be considered a human resourcing issue.

Communication Analysis

Perhaps there is a problem in communications. It is impossible to correctly fulfil a purchase order if the part number or quantity figures are copied incorrectly.

A classic example comes with a discrepancy between a verbal offer from the salesperson and inflexible back-room processes at head office. “You offered me a discount on my annual purchases”. “Our system can only provide discounts on individual bulk orders”.

Whether the customer is external or another internal department, poor communication leads to many defects.

Completion Activity

Document the results from all the analysis activities. It may be tempting to plan to use the same methodology or format for each. However, some practitioners find that each type of analysis is best presented in one format over another.

At this time, the severity of each defect should be addressed. For example, one late receipt of a required input might cost an hour of production if the material is readily available from a nearby warehouse. If, however, there is a chronic and frequent delay, caused by a systemic flaw, those “one hour” delays may amount to a serious problem…and hint at a department-wide problem.

Oskar Olofsson, 2011










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I am a Swedish-based Lean consultant, and the owner of the World-Class-Manufacturing.com web site.

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