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Design of Experiments

How to apply the statistical method called Design of Experiments (DOE) for quality improvement and research.

As a member of Minitab's Technical Support team, I get the opportunity to work with many people using DOE (Design of Experiments). People often will call after they've already chosen their design, run the experiment, and identified the important factors in their process. But now what? They have to find the best settings, but with several factors and responses, what should they do? "I wish I had a... Continue Reading
Imagine that you are watching a race and that you are located close to the finish line. When the first and fastest runners complete the race, the differences in times between them will probably be quite small. Now wait until the last runners arrive and consider their finishing times. For these slowest runners, the differences in completion times will be extremely large. This is due to the fact that... Continue Reading

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by Jasmin Wong, guest blogger   Part 1 of this two-part blog post discusses the issues and challenges in injection moulding and suggests using simulation software and the statistical method called Design of Experiments (DOE) to speed development and boost quality. This part presents a case study that illustrates this approach.  Preliminary Fill and Designed Experiment This case study considers the... Continue Reading
by Jasmin Wong, guest blogger The combination of statistical methods and injection moulding simulation software gives manufacturers a powerful way to predict moulding defects and to develop a robust moulding process at the part design phase.  CAE (computer-aided engineering) is widely used in the injection moulding industry today to improve product and mould designs as well as to resolve or... Continue Reading
Using statistical techniques to optimize manufacturing processes is quite common now, but using the same approach on social topics is still an innovative approach. For example, if our objective is to improve student academic performances, should we increase teachers wages or would it be better to reduce the number of students in a class? Many social topics (the effect of increasing the minimum... Continue Reading
Screening experimental designs allow you to study a very large number of factors in a very limited number of runs. The objective is to focus on the few factors that have a real effect and eliminate the effects that are not significant. This is often the initial typical objective of any experimenter when a DOE (design of experiments) is performed. Table of Factorial Designs Consider the table below.... Continue Reading
NOTE: This story will reveal how easy it can be to optimize settings using the statistical method called Design of Experiments, but it won't provide easy answers for making your own office coffee any better. After her team’s ultimatum about the wretched office coffee, Jill used the design-of-experiments (DOE) tool in Minitab’s Assistant to design and analyze a screening study. Jill now knew that... Continue Reading
Everyone loves a Pareto chart. That is, everyone who knows that Pareto charts are a type of bar chart ordered by bar size to help you to determine which bars comprise the vital few that you care about and which are the trivial many that you don't care about. Pareto charts are a great tool for communicating where the largest gains can be made as you focus your improvement efforts. Since I love... Continue Reading
In Blind Wine Part I, we introduced our experimental setup, which included some survey questions asked ahead of time of each participant. The four questions asked were: On a scale of 1 to 10, how would you rate your knowledge of wine? How much would you typically spend on a bottle of wine in a store? How many different types of wine (merlot, riesling, cabernet, etc.) would you buy regularly (not as... Continue Reading
Already relaxed on his first day in Napa, Brutus and his wife Suzy decide to visit their favorite winery just before lunch to taste their new Cabernet Sauvignon. The owner recognizes them as they walk in the door and immediately seats them on the patio overlooking the vineyard. Two glasses appear, and as the owner tells them about the new Cabernet, Brutus prepares for an onslaught of blackberry... Continue Reading
It’s common to think that process improvement initiatives are meant to cater only to manufacturing processes, simply because manufacturing is where Lean and Six Sigma began. However, many other industries, in particular financial services and banking, also rely on data analysis and Lean Six Sigma tools to improve processes. Rod Toro is a business process improvement manager at Edward Jones, and I... Continue Reading
The 2014 ASQ World Conference on Quality and Improvement is coming up in early May in Dallas, and this year’s International Team Excellence Award Process (ITEA) will also come to a close at the conference, as winners from the finalist teams will be chosen for ASQ gold, silver, or bronze-level statuses. What’s ITEA? The annual ASQ ITEA process celebrates the accomplishments of quality improvement... Continue Reading
The Assistant in Minitab Statistical Software includes Design of Experiments (DOE). We already spent some time looking at 5 highlights when you create a screening experiment with the Assistant in Minitab. But the Assistant can also help you make sense of the data you collect for your experiment. After you create a design with the Assistant, choose Assistant > DOE > Analyze and Interpret and you’re... Continue Reading
For me, the biggest enhancement in Minitab 17 is the addition of Design of Experiments (DOE) to the Assistant. DOE in the Assistant has so many exciting aspects it’s hard to take it all in at once, but here are 5 highlights for when you plan and create a screening experiment: 1. Just-in-time guidance If you’re lucky, you’ve had the chance to study DOE with an expert. If not, even the flow chart... Continue Reading
What factors significantly affect how quickly my couch-potato pooch obeys the “Lay Down” command? The cushiness of the floor surface? The tone of voice used? The type of reward she gets? How hungry she is? I created a 1/8 fraction Resolution IV design for 7 factors and collected response data for 16 runs. Now it’s time to analyze the data in Minitab, using  Stat > DOE > Factorial > Analyze Factorial... Continue Reading
Nala, our 6-year-old golden retriever, loves her dogma. That's her sitting in front of church on Sunday morning. But she's not crazy about her catechism. For example, she doesn't always dutifully follow the "Lay Down" commandment.   What factors may be influencing her response? We're performing a DOE screening experiment to find out. In this post, we'll use Minitab Statistical Software to Create the... Continue Reading
Design of experiments (DOE) is an extremely practical and cost-effective way to study the effects of different factors and their interactions on a response. But finding your way through DOE-land can be daunting when you're just getting started. So I've enlisted the support of a friendly golden retriever as a guide dog to walk us through a simple DOE screening experiment. Nala, the golden retriever,... Continue Reading
Recently, a customer called our Technical Support team about a Design of Experiment he was performing in Minitab Statistical Software. After they helped to answer his question, the researcher pointed our team to an interesting DOE he and his colleagues conducted that involved using nasal casts to predict the drug delivery of nasal spray. The study has already been published, and you can read... Continue Reading
All processes are affected by various sources of variations over time. Products which are designed based on optimal settings, will, in reality, tend to drift away from their ideal settings during the manufacturing process. Environmental fluctuations and process variability often cause major quality problems. Focusing only on costs and performances is not enough. Sensitivity to deterioration and... Continue Reading
The 2013 ASQ World Conference is taking place this week in Indianapolis, Indiana, and it's been a treat to see how our software was used in the projects highlighted in many of the presentations. As a supporter of the conference, a key event for quality practitioners around the world, Minitab was proud to sponsor one of the presentations that seemed to get a lot of attendees talking. Scott... Continue Reading