When you start the Measure phase, you first must identify the crucial internal processes that influence the CTQ meas- urements, which are the Y’s, the process outcomes.
Once you know what they are, then you can measure the defects generated in the process that profoundly affect the CTQ standard.
So, for example, if your customer expects a certain standard at a certain price, you need to identify the vital few factors that affect that expectation. This is crucial, since determining the
The Vital Few Equation: Y = f (x)
As you use MAIC/DMAIC, you’ll quickly realize that it
depends on the precision and accuracy of statistical analysis and mathematical formulations to succeed. Chief among these is the vital few equation:Y = f (X). So what does it mean?
Y is the outcome of a process; it is a function of X’s, the key vari- ables (the vital few factors) in a process.Y is the characteristic of qual- ity you’re trying to achieve. By identifying the X’s, you can measure, analyze, improve, and control them to achieve optimal results in the shortest time. By funneling all process elements through the equation, you will get to the vital few factors that best predict the outcome.
Once you have a predictable outcome, you can make the changes that reduce your costs. Basically, the equation lets you identify what you didn’t know—and that’s the power of Six Sigma knowledge in action.
Define Phase Deliverables
Each DMAIC phase has key deliverables that you must complete and then use as documented, quanti- fied evaluations for a project. For the Define phase, basic deliverables include the following:
1. Project status form 2. Metric graph
3. Process map with tally points 4. Pareto charts
5. Improvement plans/next steps 6. Local review
vital few allows you to concentrate your efforts and resources.
Then you must measure the impact of defects in those areas.
As you recall from Chapter 1, defects are measurable charac- teristics of a process or its output that are not within the accept- able customer limits or specifications.
Once you identify the defects, you can then ask how much money you would save if they were eliminated. In doing so, you are immediately connecting your project work to a dollar
impact—relating improved quality with improved profitability.
There is a direct and measurable relationship between defects and dollars. In the Measure phase, you can figure out that rela- tionship exactly.
The Measure phase is completed when a black belt can suc- cessfully measure the defects generated for a key process that affects the CTQ characteristic. In the Measure phase, the black belt conducts a measurement systems analysis, which includes gauge studies, and a thorough evaluation of the capability of the process.
The purpose of a gauge (or gage) repeatability and repro- ducibility study (gauge R&R) is to ensure that your measure- ment systems are statistically sound. A gauge R&R measures how you’re measuring, so you know that all aspects of your measurement systems are functioning properly and that you’re getting maximum value for your efforts. After all, you’re going to be investing a lot in rooting out the problems that your meas- urements reveal, so it makes sense to be sure that they’re accu- rate and appropriate.
A gauge R&R consists of a series of steps. They encompass calibrating your actual gauge for measurement, having various team members conduct tests on random samples in a number of trials, and finally assessing the statistical data for soundness.
Essentially, the study plays two roles:
• It can alert you to any discrepancy within defined meas- urements, so you can correct them at the beginning of projects, rather than discovering your data is flawed months later.
• It can validate that what you’re doing is credible, that you’re using metrics that not only make good sense, but also will get you the information you need to reduce or eliminate defects.
Gauge R&R repeats measurements under vari- ous conditions to test the measure against these four essential criteria:
• Accuracy.How precise is the measurement?
• Repeatability. If the same person and/or piece of equipment measures the same item more than once, will the results be the same?
• Reproducibility. If other people and/or other pieces of equipment measure the same item, will the results be the same?
• Stability. Will accuracy, repeatability, and or reproducibili- ty change over time?
Gauge R&R studies enable black belts to determine whether or not their data is accurate, repeatable, reproducible, and sta- ble—qualities essential to making any progress at all in improv- ing a process. (In some cases, your measurement analysis will show that you might be better off flipping a coin rather than using inherently flawed data! We’re reminded of that old joke about clocks, the instruments we trust to measure time. The clock that’s unreliable is less to be trusted than the clock that’s broken—because the latter is right twice a day.)
The Measure phase is all about mapping the process, evalu- ating the measurement system, using your metrics, and esti- mating the process baseline capability. It’s truly complete when your black belts can identify the vital few factors (X’s), demon-
Gauge repeatability and reproducibility study A study to ensure that your measurement systems are statistically sound.The gauge (or gage) R&R is a confidence meter of sorts! It meas- ures how you’re measuring, so you know that your systems are measur- ing accurately and appropriately.
strate the capability of the process, and establish a valid meas- urement system.
The Star Kicker
In Chapter 3, I introduced you to the field goal kicker to demonstrate the interplay of the terms specification,specifica- tion limits, capability,distribution,baseline,and defect. Now let’s take another look at the kicker in the context of DMAIC.
He can kick the ball from 50 yards to distribute it within the 18’ 6”
space between the two goal posts. However, even though he makes a good percentage of his attempts, he’s not consistent, sometimes kick- ing the ball to the left or right. He wants to concentrate on placing his kicks through the exact middle of the goal posts, so any shift won’t put his kick outside the posts.
He needs to know what Y (accurate kicking through the center) is a function of. He needs to ask questions like “What’s the angle of the ball on the ground? What is the force of my kick? How high is the ini- tial trajectory? What’s my follow-through eye and leg position?” Once he asks and answers such questions, he knows and can measure the vital few factors and take the steps necessary to control and improve his kicks for 100% precision, 100% accuracy, 100% of the time.
Measure Phase Deliverables
Each DMAIC phase has key deliverables that you must complete and then use as documented, quantified evalua-
tions for a project. For the Measure phase, basic deliverables include developing:
1. Project status form 2. Metric graph
3. Process map with tally points 4. Pareto charts
5. Measurement tools, including gauge R&R studies 6. Improvement plans/next steps
7. Local review
Once you’ve assembled this documentation, you’ll have the critical information in hand that points to exactly what and how you measured your project to isolate the vital few factors that are so central to your Six Sigma improvement efforts. It’s a disciplined approach to validating and plotting the entire course of your project.
Now that you and your teams know what the vital few fac- tors are, it’s time to move on to the Analyze phase.