Critique of Six-Sigma Research by Henderson and Evans

Introduction

The structure of a research report is straightforward. It mirrors the structure of the research itself: the problem, the methodology, the results, the conclusions, and the interpretations. The purpose of the research report is to inform readers about the problem investigated, the methods used to address that problem, the results of the investigation, and the conclusions inferred from those results (Polit & Beck, 2004). The function of the research report is not, however, to convince the reader of the virtue of the research previously conducted. At all times the report must be written so that readers can reach their own conclusions as to the adequacy of the research, the validity of the reported results, and the soundness of the conclusions. Research reports must strive to be succinct, objective, and clear. The ultimate test of an excellent research report is its ability to be replicated by those who read it. If this criterion cannot be met, the report is inadequate in terms of knowledge transfer.

The paper presented here is a thorough analysis and critique of research information reported in an article entitled "Successful Implementation of Six-Sigma: Benchmarking General Electric Company" (Henderson and Evans, 2000). The critique covers areas important to research facilitation, including — but not limited to — the methodology used, formulation of an appropriate research question, significance of the reported substantive literature, research design selection, appropriateness of sample data-gathering techniques, data analysis, and the importance of conclusions drawn.

Article Summary

Research endeavors must at all times adhere to the rigors of effective or best-fit research practice. Without stringent controls placed on the area of investigation, no research endeavor will advance any body of knowledge. To this end, all research must be finely tuned and clearly described as to its intent or purpose, the phenomenon to be assessed and reported upon, and the relevance and efficacy of the conclusions drawn.

The present article being critiqued for form and content is a thorough, in-depth description of the Six-Sigma quality control process in several selected manufacturing settings. The authors present concise and factual information about how the Six-Sigma statistical tool is implemented in a manufacturing setting and what the benefits are to using such a quality control process. However, throughout the entire article there is no discussion of the drawbacks of implementing such a system — in terms of analytical cost factors, time constraints, or the appropriateness of statistical results achieved through a Six-Sigma quality improvement process. Without presenting both sides of a theory or process, there exists a strong possibility that author bias has been introduced into the reported findings. This was found to be the case in the concluding remarks offered by the two authors.

Although Henderson and Evans present a thorough description of the statistical components of the Six-Sigma process, a full discussion of all that is presented is beyond the scope of this paper. Suffice it to say that the authors are very complete in their presentation of statistical processes — from dashboards to Kruskal-Wallis techniques to ANOVA and Chi-Square. However, caution is warranted regarding the utility of this presentation with respect to need. If the authors' purpose is to educate the reader on specific statistical processes contained within the Six-Sigma program, then an earlier declaration of purpose should have been made (Ohlson, 1998).

Research Questions, Objectives, and Methodology

Research, whether clinical, experimental, or historical, must begin with the author presenting a well-developed need for the research, followed by an answerable research question. The research question is, according to Kerlinger (1964), a result of a felt need that the author or authors present to the reader based on information offered in the opening statements of the published article. Contained within the opening statement must be the research investigator's definition of the type of research being conducted — that is, descriptive, experimental, historical, philosophical, or case study. At no point in the beginning of the manuscript was there any definitive statement as to what type of research Henderson and Evans had conducted. As a result, the reader is given no direction as to what to expect in terms of how the investigators approached the inquiry. In fact, the entire research report is essentially a thorough description of the Six-Sigma statistical process used by General Electric to determine rejection levels for acceptable and non-acceptable consumer products. The closest the investigators came to stating a researchable problem or research methodology is in their initial statement that the original goal of the Six-Sigma process is to define quality improvement as implemented by General Electric.

Although Henderson and Evans never clearly delineated what type of research they were conducting, nor did they formulate an identifiable research question, the reader can conclude independently that what was reported takes the basic form of a historical qualitative case study. Historical qualitative case research generally follows the lines of identifying certain trends that exist in the concept or phenomenon being reported upon. As such, the two investigators should have formulated a research question and hypothesis along the following lines: To what extent does there exist an increased or decreased use of the Six-Sigma quality standards process in manufacturing by General Electric? Additionally: To what extent is the Six-Sigma statistical process a viable statistical tool for determining quality standards in manufacturing via quality improvement for General Electric? Because the investigation is a case study, the researchers were not obligated to follow the research question with a testable null hypothesis, as would be required in experimental or descriptive research studies.

Conclusion and Practical Significance

All researchers are well aware that it is easy to criticize the research endeavor of another, as doing so is generally a human behavioral quality. At the same time, criticism is necessary in order to advance any body of knowledge that has found acceptance in a particular business environment. With respect to the article reviewed, the following statements are presented for the purpose of alerting others as to the efficacy of the Henderson and Evans research endeavor.

The authors failed to present the reader with a discernible research need, question, and purpose. They were unsuccessful in describing the type of research being conducted — a requirement paramount in determining the reliability and validity of a research endeavor. The authors also failed to build a base for acceptance of the research through the employment of a thorough literature review, and they did not create a need for their investigation on the basis of information garnered from such a review.

The authors were greatly remiss in convincing the reader of the efficacy of their investigation. The research presented by Henderson and Evans was simply an ad hoc presentation or review of what was taking place within the General Electric environment with respect to the Six-Sigma program. Conclusions drawn by the authors were not only scant but lacking in direction.

Although the authors describe the reasons for General Electric's adoption of a Six-Sigma program for quality improvement, they failed to present any limitations of using such a program. They were also lax in not informing the reader as to how General Electric's use of the Six-Sigma program could or could not benefit other corporations. In other words, the authors failed to present any implications for further research or use with respect to the Six-Sigma statistical process. Finally, the authors obscured their attempts to conduct effective research by simply reporting what occurs within a given corporation.

Whether or not the Henderson and Evans research endeavor has advanced any scientific body of knowledge is circumspect. This reviewer was left with the professional opinion that the same information could simply have been obtained through an examination of various internal reports generated by General Electric itself.

Practical Significance. To the unassuming reader, the information presented is impressive. Unfortunately, to the seasoned researcher — who understands that reporting existing data is simply a prelude to more sophisticated statistical data analysis — the report offers little. What the study does accomplish, however, is to serve as a wake-up call to those who want to conduct research properly. The subject matter contained in this report, although not research- and statistics-correct, is at least informative by way of its simple message: Six-Sigma is an important statistical tool for gauging quality improvement in manufacturing environments.

Henderson, Kim M., and Evans, James R. (2000). Successful implementation of Six-Sigma: Benchmarking General Electric Company. Benchmarking: An International Journal, 7(4), 260–281.

Kerlinger, Fred (1964). Foundations of Behavioral Research. New York: Holt, Rinehart and Winston, Inc.

Ohlson, E. L. (1998). Best-Fit Statistical Procedures and Research Designs. Chicago: ACTS Testing Lab.

Polit, D. F., & Beck, C. T. (2004). Research Principles and Methods (7th ed., Chapter 26). Philadelphia: Lippincott Williams and Wilkins.