Laura Ilzarbe

Practical applications of design of experiments in the field of engineering: a bibliographical review

The design of experiments (DoE) methodology is a technique that has been applied for many years in industry to improve quality. In this study, a summary of 77 cases of practical DoE application in the field of engineering is presented. All of the cases were published in important scientific journals between 2001 and 2005. The type of design that is applied, the size of the experiment, the number of factors that influence the response variable, and the sector of application of the design are analyzed. In addition, the increasing use of these designs over time is demonstrated. Copyright

Is design of experiments really used? A survey of Basque industries

A new survey is presented concerning the knowledge and use of the design of experiments technique (DoE) within industry in the Basque Country, a region recognised throughout Europe for its quality management. The survey was carried out within manufacturing companies, yielding a response rate of 18%. Results show that 94% of companies undertake experimentation; most of them use one-factor-at-a-time strategies, and only 20% of those follow a pre-established statistical methodology. Survey results show that research and development and manufacturing make up 85% of DoE use. Furthermore, results show that lack of knowledge about general statistics is commonplace and only 31% of companies claim to be knowledgeable about DoE. In addition, although Taguchi methods are well known among companies, only 7% apply this method. Despite every effort by specialists in quality and statistics, DoE has yet to be applied as widely as it could and should be.

Barriers faced by engineers when applying design of experiments

Purpose – The purpose of this article is to provide an extensive review of the barriers faced by engineers when applying design of experiments (DoE). The aim is to help new practitioners learn from the past and avoid possible barriers that they may encounter when applying DoE in industry.Design/methodology/approach – An exhaustive literary review was carried out to find articles in which hindrances to the application of DoE were mentioned. The information is organised and grouped into 16 barriers with this end in mind.Findings – The 16 barriers can be classified into three different groups: business barriers; educational barriers; and technical barriers. It is shown that DoE can be successfully applied without overcoming every barrier, although it is inconvenient to do so.Practical implications – Although DoE is commonly found in statistics and quality literature, it is clearly underused in industry. The paper brings together ideas from those with experience in DoE to detect the reasons behind this anomal...

How is experimentation carried out by companies? A survey of three European regions

A survey was carried out to characterize experimentation in three different European regions: the Baden-Wurttemberg region, The Basque Country and the rest of Spain. Results of the survey show that even though experimentation is a frequent activity, almost 95% of companies conduct experiments; the strategies used to carry them out are primitive. The one-factor-at-a-time strategy is used by 75% of companies far more than the 23%, which apply design of experiments (DoE). Results show that this may be due to the current lack of knowledge of DoE in these regions, where only 33% are familiar with the technique. Finally, the rate of applications of DoE among Six Sigma users is 40%, twice that of non-users, which stands at 19%. Copyright

Why is not design of experiments widely used by engineers in Europe

An extensive literature review was carried out to detect why design of experiments (DoE) is not widely used among engineers in Europe. Once 16 main barriers were identified, a survey was carried out to obtain first-hand information about the significance of each. We obtained 101 responses from academics, consultants and practitioners interested in DoE. A statistical analysis of the survey is introduced, including: (a) a ranking of the barriers, (b) grouping of barriers using factorial analysis, (c) differences between characteristics of respondents. This exploratory analysis showed that the main barriers that hinder the widespread use of DoE are low managerial commitment and engineers’ general weakness in statistics. Once the barriers were classified, the most important resultant group was that related to business barriers.

Planning Experiments, the First Real Task in Reaching a Goal

ABSTRACT In industrial problems, it is necessary to give importance to the whole experimental process, especially the planning stage, where there are different factors that can strongly affect the results of a study. In this article, we present a real case of DoE application, focusing on the preliminary stages of experimentation. Some of the aspects we explain in detail are how we chose the best response to analyze, how we determined what factors to evaluate, and what our data sample collection criteria were. In addition, the article contains our analysis of the experiments and details of our results.

How Hospitals Choose a Quality Management System: Relevant Criteria in Large Spanish Hospitals

This article examines the selection criteria used by hospital managers when choosing a quality management system (QMS): ISO 9001, Joint Commission (JC), EFQM, or a combination of them. Furthermore, this study provides a view of how extensive is the use of QMS in the main Spanish hospitals. Between December 2004 and March 2005, a questionnaire was sent to Spanish hospitals of size > 400 beds. Of the 101 hospitals that met the conditions of research, 42 responded to the survey: a response index of 41.58% (95% reliability and maximum margin of error of 11.6%). We have deduced the selection criteria from a contents analysis of the three models. We have confirmed two hypotheses: first, that there are 16 relevant selection criteria for hospitals when deciding on a QMS; and secondly, that they choose QMS on the basis of the priority they attribute to given selection criteria. The data lead us to the following conclusion: implementation of QMS in Spanish hospitals is quite extensive: 71.4% use ISO 9001; 11.9% JC, and 69% EFQM. The combined use of ISO 9001 and EFQM (47.6%) has also been noted. 15 of 16 criteria have been shown to be relevant, and no new criteria have been discovered.

A new design criterion for robust parameter experiments

Varying noise factors in an experiment allows us to find robust conditions against such variation. The levels of the noise factors need to be selected carefully. Levels that are too wide may be infeasible or too costly, and if too narrow they may not provide a good model for prediction and control purposes. We propose a noise-factor separation (NFS) criterion for designs used in robust parameter design, in which a design is preferred to another if it provides the same expected mean square error for the noise part of the fitted model but for a smaller range of the noise factors in uncoded units. We evaluate several experimental designs that can be used to fit a response model that is quadratic in the controllable factors and also contains noise main effects and noise × control interactions. It is shown how the new criterion is related to variance dispersion graphs for the slope and may be used in conjunction with these graphs to assess a given experimental design. The new criterion is incorporated into an optimization formulation used to find new three-level designs that also includes traditional design criteria, such a D-efficiency. A Genetic algorithm was developed to solve such formulation. It is shown how the new designs are competitive in terms of design size, noise-factor separation, and variance dispersion for the mean and slope with respect to composite mixed resolution designs.