Getting started with Six Sigma

The purpose of this step is to validate,identify and find root cause for elimination. A large numbers of potential root causes (process inputs X) of the project problems are identified via root cause analysis (example fishbone diagram). The top 3-4 potential root cause is selected using multi-voting or other consensus tools for further validation. A data collection plan is created and data are collected to establish the relative contributions of each root cause to the project metric Y. Following are the deliverables of this phase that Six Sigma Green Belts should deliver within the team:

• Statistically validate root causes
• Perform Value Stream Mapping & Process Value Analysis
• Control & Impact Matrix

Statistically Validate Root Causes

The data been collected in the Measure Phase is used to draw statistical association between CTQ causes and measures. There are a variety of statistical tools to establish these associations. Depending on the type of data discreteorcontinuous tools are selected. Z-test, t-test,2-t Test, Chi-Square Test, ANOVA, Regression, Correlation, etc., are few common hypothesis tests.

A procedure to interpret and perform all the tests is usually covered in detail in Lean Six Sigma Green Belt Training programs.

Perform Value Stream Mapping & Process Value Analysis

Value Stream Mapping (VSM) is one of the popular tools used in Lean methodology as an alternate approach to statistical way of identifying Root Causes or Process Value Analysis and in conjunction with application of Value Stream Mapping. It is used to identify the 7 types of Wastes (Muda – in Japanese) in the process. VSM is method to visually documenting the way in which value is getting built in process.

The 7 types of process wastes are generally referred to as Non-Value Added task in conventional Six Sigma. The procedure of associating every task in a process as Non-Value Adding (NVA), Value Adding (VA), or Value-Enabling (VE) is called Process Value Analysis.

These methods are very useful in projects where the extensive data collection is not possible or with Turn-Around Delays or Timereductions.

Control-Impact Matrix

The final deliverable of the Analyze phase is to summarize all findings from Process Value Analysis or Statistical validation (& VSM) in a 2×2 matrix called Control-Impact Matrix. It is important to ensure that project doesn’t end up for academic exercise or research study. Hence the Lean Six Sigma needs to identify root causes which have high impact and well within the control of the team.