The DMAIC System of Problem Solving


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Introduction

In essence, Six Sigma is driven by a progressive divide-and-conquer strategy. Where problem solving is concerned, this means starting with the immediate symptoms of an undesirable situation and then progressively isolating, optimizing and controlling the root causes.  When this cycle of improvement is connected to activity-based management methods, Six Sigma projects are the result.

When such projects share a common structure and focus, the resulting gains can be quickly aggregated in a meaningful and powerful way. By this point in time, it should be fairly clear why many noted industry (and governmental) leaders have adopted Six Sigma: It is an enabler that allows an executive to reach the “control function” of an enterprise through highly focused, data-driven projects.  The collective power of such projects unites management (and the workforce) in a pragmatic and business-centric way.

Thus, the practice of Six Sigma indirectly forces an organization to synchronously raise their company above the limitations commonly associated with disconnected fire-fighting activities that are rooted in a trial-and-error system of improvement.  However, when the Six Sigma system of business management is used to orchestrate problem solving activities, the issue of quality becomes a boardroom issue, demanding executive attention and action.  Suddenly, the needle of business starts to move in a favorable direction.

The DMAIC Process

The Six Sigma system of business management derives its power from the DMAIC improvement strategy – Define, Measure, Analyze, Improve, and Control.  Through this strategy, it is possible to improve almost anything because we reduce the problem to its deterministic root.  In other words, we apply the fundamental principle that says: Y = f (X).  Of course, this is to say that Y is the outcome and X represents all of the essential inputs, and f is the ways and means (process) by which the X’s are transformed into Y.

So, for any given problematic situation, we must define, measure, and analyze the critical Y and then improve and control the vital X’s.  To do this, we implement the DMAIC system of problem solving.  The milestones associated with each phase of the DMAIC system is described in Figure 1.0.  Essentially, the 15 steps (milestones) represents the progressive activities that must be planned and sequentially executed in order to ultimately solve a problem — and keep it solved.

Figure 1.0. The DMAIC System of Problem Solving

DMAIC Descriptions and Milestones

 Phase 1:  DEFINE

During this phase of the DMAIC process, the critical performance variables (Y’s) of a product, service, transaction, event, or activity are identified and defined.  In addition, the related performance specifications (requirements) associated with each Y must be defined or otherwise established. This means that the critical-to-quality characteristics (CTQ’s) of a deliverable must be made known, as well as their respective performance standards.  In this manner, the “ought” condition of each Y is thoroughly defined and documented.  The following tollgates should be considered as “decision thresholds.”  This means that the project reviewer should not approve continuance to the next phase until any and all tollgate deficiencies are corrected.  The following is a list of common tollgates:

  1. The business case was fully justified and approved
  2. The project success criteria were defined and approved
  3. The project closure criteria were defined and approved
  4. The project charter reflected sufficient accountability
  5. The project charter adequately defined the driving business symptom
  6. The project team was properly formed and organized
  7. The project team members were allocated sufficient work time
  8. The project was provided all necessary leadership
  9. The project was sponsored by a business executive
  10. The project execution plan was accountable and time bounded
  11. The project team was allocated sufficient resources
  12. The project work activities were adequately defined and sequenced
  13. The project activities and findings were well documented
  14. The business symptom was linked to a key deliverable
  15. The CTQs for each key deliverable were identified
  16. The performance requirements for each CTQ were defined
  17. The existing work process for each CTQ was well documented
  18. The vital lessons-learned were sufficiently documented and well presented
  19. The project achieved its phase milestones on-time and within budget
  20. The phase outcomes and project performance justified further continuance

Milestone 1.1:  Identify Problematic Output.  This milestone is related to the selection of a product or service (i.e., deliverable) that must be improved.  This means choosing a deliverable that is connected to a defined business issue or symptom.  For example, a product or service that is experiencing a field quality problem.  Of course, this type of problem could induce such symptoms as customer dissatisfaction, excessive warranty costs, or some other form of business risk.  Naturally, the selected product or service represents the focus of a Lean Six Sigma project.  The following guidelines should be considered:

  • The selected deliverable must be connected to business issue
  • The business issue (symptom) must be visible to stakeholders
  • The business issue (symptom) must be measurable and time bounded
  • The deliverable’s performance requirements must be known
  • The deliverable’s performance data must be reliable and accessible

Milestone 1.2:  Review Output History.  This milestone is related to understanding how the deliverable’s performance history factors into the current problem.  The intent is to review (i.e., explore) all of the historical connections between the selected deliverable (i.e., process output) and the driving business issue (i.e., symptom).  For example, it might be desirable to analytically correlate or otherwise relate the deliverable’s historical performance data to the business metric of interest (e.g., product capability vs. warranty cost).  In this way, the driving need for chartering a formal Lean Six Sigma project can be can be reinforced if not more fully validated (before continuing the planning and execution process).  The following guidelines should be considered:

  • Examine correlations between the deliverable and business symptoms
  • Uncover patterns (trends and cycles) of poor performance over time
  • Discover patterns (trends and cycles) of superior performance over time
  • Determine if performance expectations have been altered over time
  • Evaluate the impact of any design changes related to the deliverable

Milestone 1.3:  Describe Output Process.  This milestone is related to defining the ways and means by which the deliverable is created.  The intent is to provide a description (map) of the underlying process (work flow) that creates the selected deliverable.  In this way, the specific process steps, touch-points and actions (that yields a unit of product or service) can be visually documented for subsequent evaluation and analysis.  Often, the act of mapping the work flow (or value stream) can surface insights into the problem’s nature or its system-of-causation, thereby concluding the Lean Six Sigma project.  The following guidelines should be considered:

  • Visually document the deliverable’s existing work flow or value stream
  • Include all value-added and nonvalue-added Milestones in the process
  • Use collaborative efforts to create, review and approve the process map
  • Annotate the process Milestones with supporting information and data
  • Employ standard flow chart and mapping symbols

Phase 2:  MEASURE

During this phase of the DMAIC process, each CTQ is measured so as to establish a performance baseline.  In this manner, the “is” condition can be made known and then contrasted to the “ought” condition.  Of course, the difference between the “is” and “ought” condition of any given CTQ constitutes a performance gap, or value gap as some would say.  At all times, it must be remembered, “we can’t improve what we don’t measure.”  The following is a list of common tollgates:

  1. The process capability assessment plan (CAP) was complete and thorough
  2. The process efficiency metrics were sufficient and adequately assessed
  3. The process was evaluated for viable cost reduction opportunities
  4. The process was sufficiently evaluated for complexity reduction opportunities
  5. The process work flow was adequately documented and traceable
  6. The process work flow was evaluated for improvement opportunity
  7. The CTQ data availability study (DAS) was complete and thorough
  8. The CTQ measurement system was properly assessed and qualified
  9. The short-term CTQ capability metrics were identified and reported
  10. The long-term CTQ capability metrics were identified and reported
  11. The CTQ capability gaps were fully identified and meaningfully reported
  12. The business implications of each capability gap were assessed and reported
  13. The process capability metrics were translated into quality metrics
  14. The quality metrics were related to the process efficiency metrics
  15. The process efficiency metrics were related to key business objectives
  16. The customer’s best interests (VOC) were sufficiently assessed
  17. The provider’s best interests (VOP) were sufficiently assessed
  18. The vital lessons-learned were sufficiently documented and well presented
  19. The project achieved its phase milestones on-time and within budget
  20. The phase outcomes and project performance justified further continuance

Milestone 2.1:  Evaluate Process Efficiency.  This milestone is related to understanding how efficiently the current process actually operates.  The intent is to examine the relative efficiency associated with the deliverable’s underlying process or work flow.  This means that, once a process has been thoroughly documented (i.e., mapped), it is often desirable to evaluate or otherwise examine such things as complexity, cycle-time, operating costs and so on.  By way of such an examination, it is often possible to establish a linkage between process efficiency and effectiveness (i.e., the connection between product or service quality and process efficiency).  The following guidelines should be considered:

  • Establish the actual operating costs of the process
  • Examine the actual cycle-time of the process
  • Investigate the  actual productivity of the process
  • Correlate process efficiency metrics to product quality metrics
  • Perform gap analyses for selected process efficiency metrics

Milestone 2.2:  Qualify Measurement System.  This milestone is related to understanding how effective the measurement system actually is.  The intent is to ensure that the system of measurement provides values (i.e., measurements) that are statistically representative of the characteristic (i.e., CTQ) being investigated.  In other words, such studies are intended to verify that the measurement system is capable of providing unbiased results and minimum variation.  Of course, such objectives must be satisfied prior to the continuance of a Lean Six Sigma project.  The following guidelines should be considered:

  • Ensure that the measurement system is statistically repeatable
  • Demonstrate the measurement system is statistically reproducible
  • Verify that the measurement system provides accurate results
  • Confirm that the measurement system exhibits linearity
  • Assure that the measurement system provides stable results

Milestone 2.3Establish Output Capability.  This milestone is related to understanding how effective the process actually is.  The intent is to statistically determine the performance capability of each product or service CTQ that is selected for subsequent improvement.  In this manner, the primary improvement planning and execution activities can be better focused.  For example, a capability analysis that reveals a long-term problem with process centering would necessarily imply a set of improvement actions that would likely be quite different from those of a problem that was related to short-term process spread.  The following guidelines should be considered:

  • Select primary indices of capability (metrics) based on reporting needs
  • Develop a valid sampling plan prior to executing the capability study
  • Estimate short-term capability using accepted quality practices
  • Estimate long-term capability using accepted quality practices
  • Examine the business consequences related to the capability findings

 Phase 3:  ANALYZE

During this phase of the DMAIC process, the focus in on analyzing the performance gaps related to each selected CTQ.  Of course, the intent of this phase is to separate where the problem “is” and “is not.”  To do this, we must look for patterns of poor performance, as well as patterns of good performance.  Such patterns can provide great insight into how to the improvement effort should be continued and guided.  In addition, we must also consider any key differences or associations within and among the CTQ’s.  The following is a list of common tollgates:

  1. The process capability diagnostic plan (CDP) was complete and technically sound
  2. The primary sources (families) of CTQ variation were identified and evaluated
  3. The analytical and operational assumptions were assessed for compliance
  4. The estimates of short-term CTQ capability were free of assignable causes
  5. The short-term CTQ capability was assessed for possible autocorrelations
  6. The long-term CTQ capability was assessed for possible autocorrelations
  7. The sustainability of short-term CTQ capability was adequately evaluated
  8. The sustainability of long-term CTQ capability was adequately evaluated
  9. The CTQ design specifications were evaluated for possible modification
  10. The CTP brainstorming process focused on the primary source of CTQ variation
  11. The list of potential causes (CTPs) was properly and sufficiently developed
  12. The potential causes (CTPs) were prioritized in terms of their contributory power
  13. The CTP variable confirmation plan (VCP) was complete and technically sound
  14. The top suspect variables were thoroughly tested for contributory power
  15. The vital few CTPs were identified and rank ordered in terms of power
  16. The essential phase conclusions were rational and supported by the data
  17. The vital lessons-learned were sufficiently documented and well presented
  18. The phase best-practices were identified and adequately documented
  19. The project achieved its phase milestones on-time and within budget
  20. The phase outcomes and project performance justified further continuance

Milestone 3.1:  Diagnose Output Variation.  This milestone is related to identifying the major family of variation associated with the CTQ of interest.  The intent is to isolate the major categories of variation that underpins the current process capability.  This means the observed CTQ variations must be classified (i.e., decomposed into logical categories).  For example, the major source of variation might be within-group and not group-to-group or temporal in nature (i.e., occur over time).  Of course, this would point to a certain subset of causative variables. Thus, subsequent improvement efforts would be better focused.  The following guidelines should be considered:

  • Determine the extent to which capability is influenced by centering
  • Determine the extent to which capability is influenced by spread
  • Explore the influence of centering and spread on output quality
  • Isolate the source (category) of variation that leverages capability
  • Examine autocorrelations to uncover nonrandom patterns and trends

Milestone 3.2:  Identify Possible Causes.  This milestone is related to identifying the process variables that are suspect causes of insufficient capability.  The intent is to identify possible causes (i.e., agents) that could induce or otherwise cause process capability to change (positively or negatively).  Of course, such causes are frequently identified and prioritized through the application of structured brainstorming methods.  Naturally, these methods rely heavily on collaboration; therefore, participants must be quite familiar with the related product or service, as well as the associated process.  Historical sources of data and information are often used to supplement and guide the related activities.  The following guidelines should be considered:

  • Identify and evaluate all relevant sources of data and information
  • Focus brainstorming efforts on the major source (category) of variation
  • Employ a rational method for prioritizing all of the potential causes
  • Classify the potential causes by centering and spread influence
  • Determine if the suspect variables can be easily manipulated
Milestone 3.3:  Isolate Critical Factors.  This milestone is related to confirming the relative influence of each suspect cause (i.e., process variable).  The intent is to determine the extent to which the suspect variables can independently exert undue influence on the CTQ capability (positively or negatively).  In other words, the objective is to isolate improvement leverage by exploring the effects of competing variable settings among the array of suspect variables (i.e., contrasting different operating conditions).  The goal is to estimate the direction and magnitude of effect associated with each of the suspect variables. The following guidelines should be considered:

  • Discover the magnitude of effect associated with each suspect variable
  • Establish the direction of effect associated with each suspect variable
  • Evaluate the risk that any variable effect is due to sampling error
  • Ensure the testing assumptions are reasonably satisfied
  • Assure analytical conclusions are fully supported by the data

Phase 4:  IMPROVE

During this phase of the DMAIC process, we seek to improve the capability gap of each CTQ by close examination and improvement of the critical process Xs.  Such Xs are also called critical-to-process variables (i.e., CTPs).  Once identified, the CTPs must be set to their most optimal operating conditions.  Of course, the overall intent of this phase is to discover the “vital few” CTP relationships that drives the performance of each selected CTQ.  Hence, the goal is isolate process leverage by uncovering the CTP relationships and settings that exert undue positive (and negative) influences on the CTQ capability gaps.  Thus, a solution is identified, examined and rationally tested.  The following is a list of common tollgates:

  1. The process capability improvement plan (CIP) was complete and thorough
  2. The CIP made provisions  for the possibility of  process redesign
  3. The CIP made provisions for the possibility of product redesign
  4. The statistical effects of each CTP were appropriately evaluated and reported
  5. The practical effects of each CTP were appropriately evaluated and reported
  6. The selected CTPs were each assigned an optimal nominal specification
  7. The selected CTPs were each assigned an optimal performance tolerance
  8. The recommended CTQ capability gap solutions were subjected to pilot testing
  9. The recommended CTQ capability gap solutions were evaluated for robustness
  10. The recommended CTQ capability gap solutions were evaluated for feasibility
  11. The recommended CTQ capability gap solutions were evaluated for sustainability
  12. The essential phase conclusions were rational and fully supported by the data
  13. The solution implementation plan (SIP) was documented and well organized
  14. The SIP included provisions for a pilot implementation of the proposed solutions
  15. The SIP included a cost-benefit analysis and time bounded milestones
  16. The vital lessons-learned were sufficiently documented and well presented
  17. The phase best-practices were identified and adequately documented
  18. The project achieved its phase milestones on-time and within budget
  19. The phase outcomes and project performance justified further continuance

Milestone 4.1:  Examine Factor Effects.  This milestone is related to understanding how each CTP can directionally influence the CTQ capability.  The intent is to explore and assess all of the key effects associated with the CTPs that are known to exert undue influence on the CTQ capability.  This means that the independent and interactive effects (that surface during the course of testing and evaluation) must be statistically examined and validated in terms of direction and magnitude.  In addition, the practical and statistical conclusions must be rendered with a known degree of decision confidence.  The following guidelines should be considered:

  • Develop a test strategy that conforms to accepted quality practice
  • Ensure an appropriate sample size prior to executing the test strategy
  • Graphically examine the effect of each CTP prior to statistical analysis
  • Determine the statistical and practical significance of each effect
  • Assure the analytical conclusions are fully supported by the data

 Milestone 4.2:  Optimize Factor Settings.  This milestone is related to establishing the ideal process center for each CTP.  The intent is to prescribe a nominal operating condition (i.e., target value) for each CTP.  Of course, only those CTPs that exerts an undue influence on the CTQ capability should be considered for optimization.  The larger intent is to discover those input settings that allows substantial variations in each CTP, yet maximizes the overall CTQ capability and operating efficiency.  This action makes the CTQ capability impervious to variations in the CTPs, as well as other process variables (i.e., robustness).  Thus, the overall capability and producibility of the CTQ can be significantly enhanced.  The following guidelines should be considered:

  • Evaluate the usefulness of interactions to facilitate robustness
  • Evaluate the usefulness of nonlinearities to facilitate robustness
  • Isolate the CTP conditions that maximizes CTQ performance
  • Evaluate the selected CTP conditions in terms of process efficiency
  • Assure the analytical conclusions are fully supported by the data

Milestone 4.3:  Prescribe Factor TolerancesThis milestone is related to tolerancing the CTPs.  The intent is to prescribe operating specifications (i.e., upper and lower boundary limits) for each of the critical process variables that exert undue influence on the CTQ capability.  The larger intent is to specify a robust targeting condition and corresponding tolerances for each CTP.  This means that the process center and spread of the CTQ will not be appreciably disturbed by the short-term or long-term variations in the CTP.  In other words, the performance capability of the selected CTQ (or any other CTQ) will not be negatively impacted by CTP variations in process centering and spread (or any other potentially disturbing low-grade nonrandom process event). The following guidelines should be considered:

  • Establish a nominal performance specification (target) for each CTP
  • Establish tolerances for all nominal specifications
  • Post the performance specifications in an appropriate location
  • Develop a statistical tolerancing model to assess producibility
  • Perform tolerance simulations or worst-case analysis as needed

Phase 5:  CONTROL

During this phase of the DMAIC process, we seek to control the optimal settings of each CTP.  In this manner, the performance condition of each CTQ can be made stable over time and “robust” to normal nonrandom low-grade errors in process centering. When the settings of each CTP are truly optimal, the CTQ will be naturally “robust” or otherwise “impervious” to a limited range of variations in the corresponding CTPs.  The following is a list of common tollgates:

  1. The process capability control plan (CCP) was complete and documented
  2. The CCP is based on a defined data-driven closed-loop feedback control strategy
  3. The CCP included well defined set of CTQ monitoring guidelines and procedures
  4. The CCP included well defined set of CTP control guidelines and procedures
  5. The CCP included guidelines and procedures for CTQ capability assessment
  6. The CCP included meaningful documentation of the optimal process work flow
  7. The CCP included guidelines and procedures for evaluating process efficiency
  8. The CCP included guidelines for the periodic review of process design
  9. The CCP included a defined set of audit criteria for assuring on-going compliance
  10. The CCP included a time bounded transition plan for the process owner
  11. The impact of process improvements on existing business systems was evaluated
  12. The impact of process improvements on existing business metrics was evaluated
  13. The vital lessons-learned were sufficiently documented and well presented
  14. The phase best-practices were identified and adequately documented
  15. The project achieved its phase milestones on-time and within budget
  16. The primary project benefits were validated and approved by Phase Review
  17. The original project closure criteria were sufficiently satisfied and approved
  18. The customer related benefits were communicated to the appropriate personnel
  19. The project team members were acknowledged for their successful participation
  20. The project team members were rewarded for their successful participation

 Milestone 5.1:  Verify Solution Repeatability.  This milestone is related to assuring the solution’s on-going effectiveness.  The intent is to empirically verify that the solution can be replicated, thereby validating its effectiveness at resolving the original problem and related business issue or operational symptom.  To this end, it is often necessary to demonstrate the solution’s short-term viability and long-term feasibility to sustain improvements related to the CTQ capability.  This means the solution must resolve the underpinning problem and keep it from reoccurring over time.  The following guidelines should be considered:

  • Implement the proposed solution on a trial basis
  • Conduct periodic reviews to assess the solution’s vitality
  • Execute limited post-mortem tests to evaluate solution effectiveness
  • Execute limited post-mortem tests to assure solution stability over time
  • Evaluate the solution’s operational feasibility and efficiency

 Milestone 5.2:  Assure Process Stability.  This milestone is related to assuring on-going process stability for each CTP.  The intent is to implement a robust closed-loop feedback control system that will effectively and efficiently restrict the random and nonrandom variations associated with process operation.  In turn, this ensures that the CTQ capability will remain relatively constant and predictable over time.  Once the process has been stabilized, the practice of continuous improvement can be more effectively and efficiently implemented, thereby further enhancing process performance over time.  The following guidelines should be considered:

  • Develop a process control plan to enable the voice-of-the-process
  • Track the performance of each CTP using standard SPC methods
  • Use appropriate control limits that are properly computed and plotted
  • Make process adjustment decisions based on statistical data
  • Detect and eliminate assignable (special) causes as they occur

Milestone 5.3:  Monitor Output Capability.  This milestone is related to monitoring the deliverable’s performance (i.e., CTQ capability) over time.  The larger aim is to detect, react to and eliminate the occurrence of nonrandom variations (i.e., assignable or special causes) that could result in some form of unacceptable business risk or loss.  This means that the deliverable’s performance capability must be periodically reviewed and evaluated for compliance to standards (with a known degree of statistical confidence).  The following guidelines should be considered:

  • Develop a product control plan to enable the voice-of-the-customer
  • Track the performance of each CTQ using standard SPC methods
  • Use appropriate control limits that are properly computed and plotted
  • Make process adjustment decisions based on statistical data
  • Detect and eliminate assignable (special) causes as they occur
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Copyright 2013 Dr. Mikel J. Harry, Ltd.

About Mikel Harry

Dr. Harry has been widely recognized in many of today's notable publications as the Co-Creator of Six Sigma and the world's leading authority within this field. His book entitled Six Sigma: The Breakthrough Management Strategy Revolutionizing the World’s Top Corporations has been on the best seller list of the Wall Street Journal, New York Times, Business Week, and Amazon.com. He has been a consultant to many of the world’s top senior executives, such as Jack Welch, former CEO and Chairman of General Electric Corporation. Dr. Harry has also been a featured guest on popular television programs, such as the premier NBC show "Power Lunch." He is often quoted in newspapers like USA Today and interviewed by the media, such as The Economic Times. In addition, Dr. Harry has received many distinguished awards in recognition of his contributions to industry and society. At the present time, Dr. Harry is Chairman of the Six Sigma Management Institute and CEO of The Great Discovery, LLC.
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3 Responses to The DMAIC System of Problem Solving

  1. Pingback: The DMAIC System of Problem Solving | Mbarriger

  2. Dr. Harry, this is an excellent checklist for all Six Sigma Black Belt projects. With so many training programs out there today, sometimes what we see in the field leads us away these hard core facts.

    This is definitely a good article to file away for more Six Sigma wins in the future – for our younger practitioners learning as they grow through the ranks.

    Thank You….

  3. Fantastic,Problem solving made easy.

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