Thomas J. Lorenzen

Bio: Thomas J. Lorenzen is an academic researcher from General Motors. The author has contributed to research in topics: Expert system & Sample size determination. The author has an hindex of 9, co-authored 10 publications receiving 1559 citations.

Taguchi's parameter design: a panel discussion

Abstract: It is more than a decade since Genichi Taguchi's ideas on quality improvement were inrroduced in the United States. His parameter-design approach for reducing variation in products and processes has generated a great deal of interest among both quality practitioners and statisticians. The statistical techniques used by Taguchi to implement parameter design have been the subject of much debate, however, and there has been considerable research aimed at integrating the parameter-design principles with well-established statistical techniques. On the other hand, Taguchi and his colleagues feel that these research efforts by statisticians are misguided and reflect a lack of understanding of the engineering principles underlying Taguchi's methodology. This panel discussion provides a forum for a technical discussion of these diverse views. A group of practitioners and researchers discuss the role of parameter design and Taguchi's methodology for implementing it. The topics covered include the importance of vari...

The Economic Design of Control Charts: A Unified Approach

Abstract: The choice of control chart parameters—sample size, sampling interval, and control limits—is considered from an economic point of view. A general process model is considered, and the hourly cost function is derived. This cost function simplifies when the recorded statistics are independent. Numerical techniques to minimize this cost function are discussed, and sensitivity analyses are performed. An example illustrates the potential savings of this technique of designing control charts.

Ozone-induced changes in pulmonary function and bronchial responsiveness in asthmatics

Abstract: To compare the responses of asthmatic and normal subjects to high effective doses of ozone, nine asthmatic and nine normal subjects underwent two randomly assigned 2-h exposures to filtered, purifi...

Pulmonary responses of asthmatic and normal subjects to different temperature and humidity conditions in an environmental chamber.

Abstract: Determining the possible adverse health effects of air pollutants can be complicated by differences in the environmental conditions of temperature and humidity. To evaluate the potentially confounding effects of differences in temperature and humidity, we exposed 8 normal male subjects and 8 male subjects with asthma to the extremes in temperature and humidity that could be maintained in an environmental chamber. We performed serial pulmonary function tests for these subjects before and during 6 hr exposure periods on 5 separate occasions: cold, dry (10 degrees C, 10% relative humidity); cold, humid (10 degrees C, 50% relative humidity); normal ambient (22 degrees C, 40% relative humidity); hot, dry (37 degrees C, 15% relative humidity); and hot, humid (37 degrees C, 60% relative humidity). The exposure period included a 12 min exercise on a cycle ergometer. We found no significant change in spirometry, airways resistance, or diffusing capacity for either group of subjects at rest alone over the 6 hr period of exposure for any exposure condition. However, there were changes in spirometry and airways resistance as a result of the 12 min period of exercise. The subjects with asthma had significant decreases in forced expiratory volume in 1 sec (FEV1) (20-21%) and increases in specific airways resistance when exercising in conditions of cold and dry, cold and humid, and hot and dry. The normal subjects had an average increase in FEV1 of approximately 6% when exercising in the hot and humid conditions. We found significant correlations for the changes in FEV1 with the water content of the exposure conditions for both groups of subjects. We also found that the work performance (expressed as the external work performed divided by the oxygen consumed) was decreased for the subjects in both groups at the conditions of the higher temperature (37 degrees C) compared with the lower temperature (10 degrees C). These results confirm that controlling for the conditions of temperature and humidity is essential in chamber studies, field studies, or epidemiologic evaluations determining the adverse effect of an air pollutant.

Expert system for statistical design of experiments

Abstract: An expert system for the design and analysis of experiments includes a descriptive mathematical model of the experiment under consideration. From this mathematical model, expected mean squares are computed, tests are determined, and the power of the tests computed. This supplies the information needed to compare different designs and choose the best possible design. A layout sheet is then generated to aid in the collection of data. Once the data has been collected and entered, the system analyzes and interprets the results.

The Design and Analysis of Experiments

Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

Guidelines for methacholine and exercise challenge testing-1999. This official statement of the American Thoracic Society was adopted by the ATS Board of Directors, July 1999.

Abstract: I. Purpose and Scope II. Methacholine Challenge Testing A. Indications B. Contraindications C. Technician Training/Qualifications D. Safety E. Patient Preparation F. Choice and Preparation of Methacholine G. Dosing Protocols 1. Two-Minute Tidal Breathing Dosing Protocol 2. Five-Breath Dosimeter Protocol H. Nebulizers and Dosimeters I. Spirometry and Other End-point Measures J. Data Presentation K. Interpretation III. Exercise Challenge A. Indications B. Contraindications and Patient Preparation C. Exercise Challenge Testing D. Assessing the Response References Appendix A: Sample Methacholine Challenge Test Consent Form Appendix B: Sample Methacholine Challenge Pretest Questionnaire Appendix C: Sample Report Format Appendix D: Equipment Sources