Critique of Six-Sigma Research by Henderson and Evans

Introduction

The rules for evaluating a researcher's investigative endeavor are closely guided by a code of research ethics to which the writing and investigation must adhere — namely objectivity, subject knowledge, and professionalism. The article authored by Henderson and Evans and subjected to review here concerns the Six-Sigma statistical process employed to evaluate manufacturing quality improvement.

The article was carefully scrutinized with respect to proper research formatting. A definitive evaluation was conducted in terms of identifying a proper research question, need and problem statement, appropriate data analysis, and the effectiveness of the summary conclusions drawn. Unfortunately, the article critiqued is not a true research endeavor, as the authors failed to adhere to the stringent rules governing research investigations. The totality of the information presented is simply a reporting of what is currently taking place in a large corporation with respect to quality improvement.

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.

Article Summary

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.

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.

Research Questions, Objectives, and Methodology

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, 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.