Rare events inherently occur in all kinds of
processes. In hospitals, there are medication errors, infections,
patient falls, ventilator-associated pneumonias, and other rare,
adverse events that cause prolonged hospital stays and increase
But rare events happen in many
other contexts, too. Software developers may need to track errors
in lines of programming code, or a quality... 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
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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
Histograms are one of the
most common graphs used to display numeric data. Anyone who
takes a statistics course is likely to learn about the histogram,
and for good reason: histograms are easy to understand and can
instantly tell you a lot about your data.
Here are three of the most important things you can learn by
looking at a histogram.
Shape—Mirror, Mirror, On the Wall…
If the left side of a... 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
my last post covered
statistical tools for the Process Design stage, here we will
focus on the statistical techniques typically utilized for the
second stage, Process Qualification.
Stage 2: Process... 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
Process validation is vital to the success of companies that
manufacture drugs and biological products for people and animals.
According to the FDA guidelines published by the U.S. Department of
Health and Human Services:
“Process validation is defined as
the collection and evaluation of data, from the process design
state through commercial production, which establishes scientific
evidence that a... 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
The ultimate goal of most quality improvement projects is clear:
reducing the number of defects, improving a response, or making a
change that benefits your customers.
We often want to jump right in and start gathering and analyzing
data so we can solve the problems. Checking your measurement
systems first, with methods like attribute agreement analysis or
Gage R&R, may seem like a needless waste... Continue Reading
To assess if a process is stable and in statistical control, you
can use a control
chart. It lets you answer the question "is the process that you
see today going to be similar to the process that you see
tomorrow?" To assess and quantify how well your process falls
within specification limits, you can use capability
Both of these tools are easy to use in Minitab, but you
first need to... Continue Reading
when I used to work in Minitab Tech Support, customers often asked
me, “What’s the difference between Cpk and Ppk?” It’s a good
question, especially since many practitioners default to using Cpk
while overlooking Ppk altogether. It’s like the '80s pop
duo Wham!, where Cpk is George Michael and Ppk is that other
Poofy hairdos styled with mousse, shoulder pads, and leg warmers
aside, let’s... Continue Reading
Design of Experiments (DOE) is the perfect tool to efficiently
determine if key inputs are related to key outputs. Behind the
scenes, DOE is simply a regression analysis. What’s not simple,
however, is all of the choices you have to make when planning your
experiment. What X’s should you test? What ranges should you select
for your X’s? How many replicates should you use? Do you need
center... Continue Reading
outlier is an observation in a data set that lies a substantial
distance from other observations. These unusual observations can
have a disproportionate effect on statistical analysis,
such as the mean, which can lead to misleading results.
Outliers can provide useful information about your data or process,
so it's important to investigate them. Of course, you have to find
Finding... Continue Reading
Suppose you’ve collected data on cycle time, revenue, the
dimension of a manufactured part, or some other metric that’s
important to you, and you want to see what other variables may be
related to it. Now what?
When I graduated from college with my first statistics degree,
my diploma was bona fide proof that I'd endured hours and hours of
classroom lectures on various statistical topics, including
Getting your data from Excel into Minitab Statistical
Software for analysis is easy, especially if you keep the
following tips in mind.
Copy and Paste
To paste into Minitab, you
can either right-click in the worksheet and
Cells or you
can use Control-V. Minitab allows for 1 row of
column headers, so if you have a single row of column info (or no
column header info), then you can quickly... Continue Reading
Leading and trailing spaces in a data set are like termites in
your house. If you don’t realize they are there and you don’t get
rid of them, they’re going to wreak havoc.
are a few easy ways to remove these pesky characters with Minitab Statistical
Software prior to analysis.
If you’re importing data from Excel, a text file, or some other
Choose File > Open and select
your... Continue Reading
You have a column of categorical data. Maybe it’s a column of
reasons for production downtime, or customer survey responses, or
all of the reasons airlines give for those riling flight delays.
Whatever type of qualitative data you may have, suppose you want to
find the most common categories. Here are three different ways to
1. Pareto Charts
Pareto Charts easily help you separate the vital...Continue Reading
If you need to assess process
performance relative to some specification limit(s),
capability is the tool to use. You collect some accurate
data from a stable process, enter those measurements in Minitab,
and then choose Stat > Quality Tools >
Capability Analysis/Sixpack or Assistant
> Capability Analysis.
Now, what about sorting the data?
I’ve been asked “why does Cpk change when I... Continue Reading
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