Six Sigma overview
Source: What is Six Sigma?, Pete Pande and Larry Holpp, McGraw-Hill, 2002.
What is Six Sigma?
Six Sigma is a quality system based on measurements of how well an organization meets customer requirements. “Sigma” refers to a statistical measure of variance, which is measured on a scale as follows:
(Sigma) rating Σ( 0 1 2 3 4 5 6 Defect rate 93.32% 69.15% 30.85% 6.68% .62% .23% .034% On-time at-quality rate 6.68% 30.85% 69.15% 93.32% 99.38% 99.77% 99.966%
The “six” in sigma refers to the highest possible sigma rating, which indicates that a product or service meets all the customers’ time and quality criteria (delivery “on-time and at-quality”) 99.966% of the time. This scale recognizes that no process can deliver 100% quality at all times, so 6 is the highest possible sigma rating. These time and quality criteria can be applied to virtually any product or service, so Six Sigma tools can be used in any type of organization that has customers. Six Sigma provides a methodology and a set of tools that help organizations to assess their current level of quality and then improve delivery to customers incrementally, one sigma level at a time. Six Sigma is distinguished from other quality systems by several themes: • • • • Focus on the customer rather than process, inputs, or outputs. The sigma level is determined by how well the organization and its processes meet customer requirements. Data- and fact-driven management, with an emphasis on measurement of quantitative data. Process is the key vehicle of success. Six Sigma tools are applied to create major process changes, not only incremental improvements, in order to improve quality. Proactive management. Implementing Six Sigma in an organization requires a high level of management buy-in (often at the executive level or higher) and management “champions” are held directly accountable for the effort’s success. The work is delegated, but accountability is not. Emphasis on root causes, digging down beyond proximal causes to find what is really going on. Creating sustained changes, with control mechanisms in place to ensure changes are sustained over the long term.
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Six Sigma Methodology
Six Sigma’s 5 major steps make the acronym DMAIC (duh-MAY-ick):
D: Define 1. 2. 3. 4. M: Measure 1. 2. 3. A: Analyze I: Improve 1. 2. • • • • • C: Control • • • • • • Ask who, what, and why questions about the project Write the project charter (includes a business case, problem/opportunity statement, goal statement, constraints/assumptions, scope, players/rules, and a preliminary plan) Identify the customer and translate the “voice of the customer” into requirements to measure against Create a high-level process diagram Gather data on outputs/outcomes, processes, and inputs Identify facts and data that offer clues to quality issues Create an early sigma measure of the process Analyze the data, using advanced statistics and tools as needed Find the root cause of quality issues Solution and action stage: solve the problem and act on it May go back to the Charter to modify problem/goal statement to reflect discoveries May confirm with the Champion May modify the scope of the project Implement, manage, and test solutions. Usually, solutions will be thoroughly piloted and tested before full implementation. Develop and implement monitoring process to track changes and results Create response plan in case solutions do not work as intended Help management focus on appropriate metrics to get info on outcomes and processes “Sell” project throughout organization Handoff responsibilities to day-to-day operations staff Ensure management support for long-term goals
Typical Six Sigma Project Life Cycle
1. Identify/select project(s). Ensure they meet the “Two M’s”: meaningful and manageable. Articulate the business necessity of the project. 2. Form the Six Sigma team: choose a Black Belt or Green Belt leader and 5-6 members. 3. Develop the charter. This is usually drafted by the Champion and edited/added onto by the team; it is a dynamic document that evolves throughout the project. 4. Train the team. The focus of training is on the DMAIC process and tools, and totals 1-4 weeks. Typically, teams go through a full week of training, with second and subsequent training sessions following 2-5 weeks of “intersession” work on the project. 5. Do the project and implement solution(s). 6. Hand off solution(s) to appropriate stakeholders. This usually takes place in a formal ceremony with the Six Sigma team, process owner(s), and stakeholders.
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Six Sigma roles
Six Sigma establishes a variety of colorfully-named roles throughout the organization. It is rumored that one of the developers of Six Sigma (at the Motorola corporation) was a fan of karate and borrowed the “belt” nomenclature from his favorite sport.
Title Black Belt Role • Most critical role. Without a qualified Black Belt, the process will usually fail. • Skilled in Six Sigma methodology, tools, and processes • Leads a Six Sigma team • Serves for 18 months to 2 years • Carries out 4-8 projects Experience and skills • Usually developed from within the organization, but reassigned full-time to Six Sigma project. • Usually middle manager or a future manager being developed • Problem solving • Data collection and analysis • Organizational savvy • Leadership/coaching • Understanding of administrative systems and processes • Often a professional Six Sigma consultant • Substantial experience with all areas mentioned under Black Belt
Master Black Belt
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Green Belt
Champion or Sponsor
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Implementation Leader
Coach, mentor, and trainer to Black Belts Expert in Six Sigma methodology, tools, and processes Offers hands-on help to Black Belts Similar to Black Belt, but holds a regular position while participating in or leading a Six Sigma team Brings methodology to the day-today work of the organization Initiates and sponsors a Black Belt or team project Directly accountable for project results Aligns project with business goals Orchestrates entire Six Sigma effort within an organization
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Similar to Black Belt
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Executive-level or key operational manager Often member of organization’s Leadership Council or steering committee Corporate VP reporting to chief executive Often a seasoned professional in quality or organizational improvement hired specifically for Six Sigma effort May be an experienced executive from within the organization
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Black Belts and Master Black Belts are often certified in Six Sigma, but there is no universal or official certification standard.
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Six Sigma Toolkit
Six Sigma utilizes a variety of existing project management, statistical, and analysis tools. Idea generation tools • Brainstorming • Affinity diagrams • Multivoting • Structure tool • SIPOC (supplier, input, process, output, customer) diagrams • High-level process maps • Flowcharts • Fishbone diagrams Data gathering tools • Statistical sampling • Operational definitions • VOC (Voice of the Customer) methods • Checklists • Spreadsheets • MSA (measurement systems analysis) Process and data analysis • Process-flow analysis • Charts and graphs Statistical analysis • Tests of statistical significance: chi-square, t-test, analysis of variance • Correlation/regression • Design of experiments Implementation and process management • Project management methodologies • Potential problem analysis • Failure mode and effects analysis • Stakeholder analysis • Force field diagrams • Process documentation • Balanced scorecards • Process dashboards
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