Choosing the right type of subgroup in a control chart is
crucial. In a rational subgroup, the variability within a subgroup
should encompass common causes, random, short-term variability and
represent “normal,” “typical,” natural process variations, whereas
differences between subgroups are useful to detect drifts in
variability over time (due to “special” or “assignable” causes).
Variation within... Continue Reading
You run a capability analysis
and your Cpk is bad. Now what?
First, let’s start by defining
what “bad” is. In simple terms, the smaller the Cpk, the more
defects you have. So the larger your Cpk is, the
practitioners use a Cpk of 1.33 as the gold standard, so we’ll
treat that as the gold standard here, too.
Suppose we collect some data and run a capability analysis using
In Part 1 of Gauging Gage, I looked at how adequate a
sampling of 10 parts is for a Gage R&R Study and providing
some advice based on the results.
Now I want to turn my attention to the other two factors in the
standard Gage experiment: 3 operators and 2 replicates.
Specifically, what if instead of increasing the number of parts in
the experiment (my previous post demonstrated you would need... Continue Reading
by Kevin Clay, guest blogger
In transactional or service processes, we often deal with
lead-time data, and usually that data does not follow the normal
Consider a Lean Six Sigma project to reduce the lead time
required to install an information technology solution at a
customer site. It should take no more than 30 days—working 10 hours
per day Monday–Friday—to complete, test and... Continue Reading
"You take 10 parts and have 3 operators measure each 2
This standard approach to a Gage R&R experiment is so
common, so accepted, so ubiquitous that few people ever question
whether it is effective. Obviously one could look at whether
3 is an adequate number of operators or 2 an adequate number of
replicates, but in this first of a series of posts about
"Gauging Gage," I want to look at... Continue Reading
In Part 1 of this blog series, I
compared Six Sigma to a diamond because both are valuable, have
many facets and have withstood the test of time. I also explained
how the term “Six Sigma” can be used to summarize a variety of
concepts, including philosophy, tools, methodology, or metrics. In
this post, I’ll explain short/long-term variation and
between/within-subgroup variation and how they help... Continue Reading
you know the most popular diamond cut is probably the Round
Brilliant Cut? The first early version of what would become the
modern Round Brilliant Diamond Cut was introduced by an Italian
named Vincent Peruzzi, sometime in the late 17th century. In
the early 1900s, the angles for an "ideal" diamond cut were
designed by Marcel Tolkowsky. Minor changes have been made
since then, but the angles... Continue Reading
In its industry guidance to companies that manufacture drugs and
biological products for people and animals,
the Food and Drug Administration (FDA) recommends three stages for
Process Qualification, and Continued Process Verification. In
this post, we we will focus on that third stage.
Stage 3: Continued Process Verification
Per the FDA guidelines, the goal of... Continue Reading
To make objective
decisions about the processes that are critical to your
organization, you often need to examine categorical data. You may
know how to use a t-test or ANOVA when you’re comparing measurement
data (like weight, length, revenue, and so on), but do you know how to compare
attribute or counts data? It easy to do with statistical software
One person may look at
this bar... Continue Reading
Have you ever wished your control charts were better? More
effective and user-friendly? Easier to understand and act
on? In this post, I'll share some simple ways to make SPC
monitoring more effective in Minitab.
Common Problems with SPC Control Charts
worked for several years in a large manufacturing plant in which
control charts played a very important role. Virtually thousands of
SPC... Continue Reading
In my last post on
DMAIC tools for the Define phase, we reviewed various graphs
and stats typically used to define project goals and
customer deliverables. Let’s now move along to the tools you can
use in Minitab
Statistical Software to conduct the Measure phase.
Measure Phase Methodology
The goal of this phase is to measure the process to
determine its current performance and quantify the problem.... Continue Reading
People frequently have different opinions. Usually that's
fine—if everybody thought the same way, life would be pretty
boring—but many business decisions are based on opinion. And when
different people in an organization reach different conclusions
about the same business situation, problems follow.
Inconsistency and poor quality result when people being asked to
make yes / no, pass / fail, and... Continue Reading
Ahoy, matey! Ye’ve come to the right place to learn about Value
Stream Maps (VSM). Just as a treasure map can lead a band o’
pirates to buried treasures, so too can the VSM lead a process
improvement bilge rat to the loot buried deep inside a process!
Minitab has an easy-to-use VSM tool to guide yer way.
value stream map to illustrate the flow of materials and
information as a... Continue Reading
we enter late December, snow is falling here on the East Coast of
the United States. The official start to winter is on December 21,
2016, but it’s certainly not uncommon to see snowflakes flying
before this date.
If you live in the U.S., you know the winter of 2015 was one for
the record books. In fact, more than 90 inches of snow fell in
Boston in the winter of 2015! Have you ever wondered how... Continue Reading
The line plot is an incredibly
agile but frequently overlooked tool in the quest to better
understand your processes.
In any process, whether it's baking a cake or processing loan
forms, many factors have the potential to affect the outcome.
Changing the source of raw
materials could affect the strength of plywood a factory produces.
Similarly, one method of gluing this plywood might be better... Continue Reading
If you’re familiar with Lean Six Sigma, then you’re familiar
DMAIC is the acronym for Define, Measure, Analyze, Improve and
Control. This proven problem-solving strategy provides a structured
5-phase framework to follow when working on an improvement
This is the first post in a five-part series that focuses on the
tools available in Minitab Statistical
Software that are most... Continue Reading
Reliability analysis is the perfect tool for calculating the
proportion of items that you can expect to survive for a specified
period of time under identical operating conditions. Light bulbs—or
lamps—are a classic example. Want to calculate the number of light
bulbs expected to fail within 1000 hours? Reliability analysis can
help you answer this type of question.
But to conduct the analysis... Continue Reading
If your work involves quality improvement, you've at least
heard of Design of Experiments (DOE). You probably know
it's the most efficient way to optimize and improve your process.
But many of us find DOE intimidating, especially if it's not a tool
we use often. How do you select an appropriate design, and ensure
you've got the right number of factors and levels? And after you've
gathered your... Continue Reading
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