Quality Improvement

Blog posts and articles about using statistics and data analysis to improve quality through methodologies such as Lean and Six Sigma.

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 like Minitab.  One person may look at this bar... Continue Reading
Genichi Taguchi is famous for his pioneering methods of robust quality engineering. One of the major contributions that he made to quality improvement methods is Taguchi designs. Designed experiments were first used by agronomists during the last century. This method seemed highly theoretical at first, and was initially restricted to agronomy. Taguchi made the designed experiment approach more... Continue Reading

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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 validation. While 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
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 I 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 the first part of this series, we saw how conflicting opinions about a subjective factor can create business problems. In part 2, we used Minitab's Assistant feature to set up an attribute agreement analysis study that will provide a better understanding of where and when such disagreements occur.  We asked four loan application reviewers to reject or approve 30  selected applications, two... Continue Reading
Previously, I discussed how business problems arise when people have conflicting opinions about a subjective factor, such as whether something is the right color or not, or whether a job applicant is qualified for a position. The key to resolving such honest disagreements and handling future decisions more consistently is a statistical tool called attribute agreement analysis. In this post, we'll... 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’s Quality Companion has an easy-to-use VSM tool to guide yer way. Use a value stream map to illustrate the flow of materials... 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 with DMAIC. 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 project. 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
A member of Minitab's LinkedIn group asked how to create a chart to monitor change by month, specifically comparing last year's data to this year's data. My last post showed how to do this using an Individuals Chart of the differences between this year's and last year's data.  Here's another approach suggested by a participant in the group.  Applying Statistical Thinking An individuals chart of the... 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
In Parts 1 and 2 of this blog series, I wrote about how statistical inference uses data from a sample of individuals to reach conclusions about the whole population. That’s a very powerful tool, but you must check your assumptions when you make statistical inferences. Violating any of these assumptions can result in false positives or false negatives, thus invalidating your results.  The common... Continue Reading
Pareto charts are a special type of bar chart you can use to prioritize almost anything. This makes them very useful in making sound decisions. For example, if you have several possible quality improvement projects, but not enough time or people to do them all now, you can use a Pareto chart to identify which projects have the most potential for making meaningful improvement. Pareto charts look... Continue Reading
At the inaugural Minitab Insights Conference in September, presenters Benjamin Turcan and Jennifer Berner discussed how to present data effectively. Among the considerations they discussed was choosing the right graph. Different graphs are good for different things. Of course, opinions about which graph is best can, and do, differ. Dotplot devotees might decide that they are demonstrably... 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
No matter how experienced you are at analyzing data, communicating about your results can be a tremendous challenge. So it's not surprising that "Effectively Reporting Your Data Analysis" was one of the best-attended sessions at the inaugural Minitab Insights Conference last month.  The presenters, Benjamin Turcan and Jennifer Berner of First Niagara Bank, have a great deal of experience improving... Continue Reading
Every day, thousands of people withdraw extra cash for daily expenses. Each transaction may be small, but the total amount of cash dispersed over hundreds or thousands of daily transactions can be very high. But every bank branch has a fixed cash flow, which must be set without knowing what each customer will need on a given day. This creates a challenge for financial entities. Customers expect... Continue Reading
A reader asked a great question in response to a post I wrote about Pareto charts. Our readers typically do ask great questions, but this one turned out to be more difficult to answer than it first seemed. My correspondent wrote:  My understanding is that when you have count data, a bar chart is the way to go. The gaps between the bars emphasize that the data are not measured on a continuous scale.... Continue Reading