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Design of Experiments

Case Study: Using DFSS and DOE to Increase Product Reliability

A medical devices company, developing technology to enable smaller medical devices, launched a substrate development effort as part of a larger-scale technology and product development effort. The substrate development effort involved predicting the stress caused by the laser welding process to ensure product reliability. In this Design for Six Sigma (DFSS) case study, design and…

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When and How to Use Plackett-Burman Experimental Design

Plackett-Burman experimental design is used to identify the most important factors early in the experimentation phase when complete knowledge about the system is usually unavailable. Developed in 1946 by statisticians Robin L. Plackett and J.P. Burman, it is an efficient screening method to identify the active factors using as few experimental runs as possible. In…

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Design of Experiments – A Primer

Design of experiments (DOE) is a systematic method to determine the relationship between factors affecting a process and the output of that process. In other words, it is used to find cause-and-effect relationships. This information is needed to manage process inputs in order to optimize the output. An understanding of DOE first requires knowledge of…

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Design of Experiments for Software Testing

When DOE (design of experiments) is used for software testing, there is a large amount of savings in testing time and cost. Various users in automotive, telecommunication and defense industries report big productivity improvements to their traditional testing methods. This success is due to two major important factors: 1) focused attention on the usage of…

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Most Practical DOE Explained (with Template)

For purposes of learning, using, or teaching design of experiments (DOE), one can argue that an eight run array is the most practical and universally applicable array that can be chosen. There are several forms of and names given to the various types of these eight run arrays (e.g., 2^3 Full Factorial, Taguchi L8, 2^4-1…

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Three Romeos and a Juliet – An Early Brush with DOE

Three young men, each being infatuated with the same woman, agree to conduct a design of experiment (DOE) of love. Statistics and romance intertwine in this entertaining and educational real-life story. Which bachelor will end up with the young lady’s hand? Will the DOE prove successful? Peeping into my youthful past, I recall three close…

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The Importance of Statistical Thinking

Six Sigma is the buzzword of today. Companies big and small talk about it and numerous success stories further advertise its relevance in today’s challenging business environment. Debates on its emergence as a strategic initiative have created critics who consider it old wine in a new bottle and loyal followers willing to swear by it….

Save Time With Fractional Factorial DOEs

Design of experiments (DOE) is a key tool in the Six Sigma methodology. DOEs help improve processes in a quantum fashion, and is an approach for effectively and efficiently exploring the cause and effect relationship between numerous process variables (Xs) and the output or process performance variable (Y). DOE helps in the following ways: The…

From Quality Control to Quality Improvement

Everybody is familiar with control charts for quality control. An example of a control chart is shown below. In the example a packaging company who made blisters for the pharmaceutical industry found the process average for a critical characteristic was out of control. There were some ideas about possible causes but, as in most other…

Reducing Variability With DOE

Six Sigma is the new rallying cry for quality improvement in the process industry. For example, Dow aims to generate an extra $1.5 billion per year in profits after training 50,000 of their employees on the methods of Six Sigma.3 Statistical tools play a key role in achieving savings of this magnitude. In fact, sigma…

Design For Six Sigma Roadmap

In the 21st century, new technologies will be developed and improved and will eventually be obsolete for the need of more advanced technologies. In this dynamically changing world, product cycles are expected to last for just a few months. To meet these demanding requirements product developers have to develop products in the shortest amount of…

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Process, Product and People: 3P Approach to Quality

Quality management should be a holistic approach. Process, product and people are the three key elements of a company’s quality system and all of them need to be focused on for an overall improvement in performance. Process Process audits and statistical process control are two important tools that practitioners can use for process monitoring. Audits…

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Decision-Making with Cause-and-Effect Analysis and DOE

Business process improvements, the grail of any company’s operations, translate directly into better profits by cutting costs and increasing competitiveness at the same time. In many cases, business process improvements have accelerating cumulative effects on company profits. If an insurance company, for example, can underwrite policies faster or settle claims faster, it is providing better…

Designing and Analyzing Experiments with Mixtures

In the development phase of Design for Six Sigma (DFSS), practitioners who work in domains such as medical devices, pharmaceuticals, foods, material composition and semiconductors frequently deal with experiments to determine optimal ingredient mixtures for desired products. The factors in a mixture experiment are the ingredients or components of a mixture, and the response is…

Design of Experiments/Conjoint Analysis in Marketing

The application of Six Sigma to marketing should be the most obvious use in the world. Where else does there exist such a direct connection between the wants and needs of the customer and the products or services a company offers? However, at first glance, there would seem to be very little hard reliable data…

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DOE in Software Testing: The Potential and the Risks

Testing software is hard work. Many aspects of software systems are difficult or impossible to observe and measure directly. That makes finding defects, characterizing performance and estimating reliability the toughest parts of the development process. While there are no silver bullets (and no “lead bullets” either, as per Dr. Barry Boehm, noted software engineering professor…

Analyzing Experiments with Ordered Categorical Data

Six Sigma projects in various industries often deal with experiments whose outcomes are not continuous variable data, but ordered categorical data. Analysis of variables (ANOVA) is a technique used to analyze continuous experimental data, but is not adequate for analyzing categorical experimental outcomes. Fortunately, many other methods have been developed to deal with categorical experiments,…

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Role for Design of Experiments in Financial Operations

Most Master Black Belts would probably cite design of experiments (DOE) as the most underused statistical tool in financial services. Yet, designed experiments are a favorite tool of statisticians and Six Sigma practitioners working in general business environments because they are an extremely efficient way of identifying what matters in a process and what does…

Teaching DOE Using Formula Fuelers Toy Motorcycles

When teaching Design for Six Sigma (DFSS), one of the challenges was that some of the trainees had been through Green Belt and Black Belt DMAIC (Define, Measure, Analyze, Improve, Control) training. On the topic of design of experiments (DOE), they were familiar with the statapult exercise and were either bored with the contraption or…

DOE for Services: Right Training Makes It a Valuable Tool

When it comes to mastering design of experiments (DOE), many quality professionals experience a steep learning curve. DOE can be complex, and to fully understand and apply it, professionals need to learn when to use it, how to set up the experimental design and how to interpret their results.  Service quality professionals face an even…

DOE: The ‘Power Tool’ of the Analyze and Improve Phases

Even a novice on a Six Sigma project team knows each step in the basic five-step DMAIC method (Define, Measure, Analyze, Improve, Control) is essential to the success of a breakthrough project. What is not as widely recognized, however, is that each step brings a distinct set of tools to bear on the project objective….

Importance of Test Plans/Test Protocol (with a Template)

Test plans, also called test protocol, are formal documents that typically outline requirements, activities, resources, documentation and schedules to be completed. Some form of test plan should be developed prior to any test. The key reasons for developing test plans are: Preparation: To assure that all reasonable aspects of running a test have been considered….

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