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WRITING A SCIENTIFIC REPORT

by Jon Wong,

Department of Environmental Toxicology, University of California-Davis.

The material and information provided in this handout are excerpts from the textbook How to Write and Publish a Scientific Paper, 2nd ed., Robert A. Day, ISI Press, 1983, Philadelphia, PA. and from the article by Berry, R. E.; Noyes, O. R. How to get your paper published in Journal of Food Science, Journal of Food Science, 1993, 58 (5), 1179-1184.

Abstract

The abstract states the principal objectives and scope of the investigation, describes the methodology employed, and summarizes the results and principal conclusions. References to the literature must not be cited in the abstract (except in rare instances, such as modification of a previous published method). Forget about all the experimental detail, omit all the references from previous works, and avoid all the lengthy exposition of your detailed knowledge of the specific problems investigated. Try to limit yourself to a short description of the problem and its solution. A well-written abstract allows the reader to identify the basic content of the document quickly and accurately, to determine its relevance to his/her interests, and decide whether he/she need to read the document in its entirety. To write an effective abstract, use brief statements of the nature of the problem, state your hypothesis, give a general approach, and present your results and conclusions. Limit your abstract to about half a page of text or about 150 words.


Introduction

The purpose of the introduction is to supply sufficient background information to allow the reader to understand and evaluate the results of the present study without needing to refer to previous publications on the topic. The introduction provides the rationale for the present study. It should briefly and clearly state your purpose in writing the paper. References must be carefully chosen to provide the most important background information. The introduction should contain (i) short paragraphs that describe the nature and scope of the problem investigated, (ii) review the pertinent literature to orient the reader, and (iii) state the method of the investigation or reasons for the choice of a particular method. For the introduction, give short paragraphs about the importance and nature of the problem, briefly state what's been done before, how this approach differs, remaining problems, your hypothesis, and objective of the current study.

Materials and Methods

The main purpose of the Materials and Methods section is to present enough detail that a competent worker can repeat the experiments. Careful writing of this section is critically important because the cornerstone of the scientific method requires that your results be reproducible. The potential for producing the same or similar results must exist, or your paper does not represent good science. If there is serious doubt that your experiments could be repeated, the reviewer will recommend rejection of your paper, no matter how awe-inspiring your results.

For the materials, include the exact technical specifications and quantities and source or method of preparation. It may be necessary to list pertinent chemical and physical properties of reagents or chemicals used. Avoid using trade names, use the generic or chemical names instead. Because the value of your paper and your reputation can be damaged if your results are not reproducible, you must describe research materials with great care.

For methods, the usual order of presentation is chronological. For measurements, be precise as possible. Questions such as "how" and "how much" should be precisely answered by the author and not left for the reader to puzzle over. If your experimental method is new, you must provide all of the needed detail. However, if the method has been previously published, only the literature reference should be given. If alternative methods are employed, identify the methods or alterations, as well as cite the reference.

Summing things up, state what you did and how you did it in a way that a reader can repeat the study. Do not include discussion, rationale, excuses, etc. Describe methods used for statistical analysis. Do not include in the materials and methods why you conducted the study, how it turned out, how you interpreted the results, or the rationale. All of these should be in the results and discussion section. The only purpose for the Materials and Methods is to provide enough information so that the experiments could be reproduced by a competent colleague.

Results and Discussion

Most authors choose to write the results and discussion together in a single section. The choice is up to the writer (or the instructions of the instructor or journal) whether the separation of the results and discussion into two distinct section is necessary and appropriate. The Results should contain two goals. First, you should give some kind of overall description of the experiments, providing the "big picture" without, however, repeating the experimental details previously provided in Materials and Methods. Second, you should present the data. The presentation of the data is important because you must and unambiguously illustrate your results before you can effectively discuss and present your conclusions.

As a general rule, present the results that best clarify the important points of your discussion. If you made only a few determinations of your results, give the results in the text. Also, presentation of raw data such as peak areas from a chromatograph or optical density readings from a spectrophotometer are not results. Raw data should be presented in an appendix. If your results are calculated from a mathematical expression, sample calculations are presented in the appendix but the mathematical expression and the resulting calculations are presented in the Results and Discussion.

The Discussion is usually the most difficult part to write. The components of a good Discussion usually contain these elements:

1. Presentation of the principles, relationships and generalizations shown by the Results.

2. Point out any exceptions or lack of correlation and define any unsettled points. Try to explain why those specific or unsettled points do not correlate, and suggest what you can do to avoid these lack of correlations if experimental errors were involved.

3. Show how your results and interpretations agree or contrast with previously published work. Try to present reasonable explanations why your results do not agree with comparable results by other researchers.

4. Discuss the theoretical implications of your work as well as practical applications. This provides the basis on why your work is important and why your investigations are important in context with other people's research.

5. State your conclusions as clearly as possible and summarize your evidence for each conclusion.

In summary, what did you find? How do results relate to those reported previously? Was the hypothesis correct? Does it need to be changed and what are the appropriate changes? Are all tables, graphs, and other illustrations absolutely necessary to understand the study? Is information in the tables, graphs, and text redundant or repetitive? Are statistical differences/significances clear?

Conclusion

For the conclusion, did you answer the question, "So what?" What recommendations/advice to the reader can you make on the basis of your findings? Do you need to adapt your hypothesis or extend it?

References and Citation

References must substantiate, relate to, or confirm the assumptions in your study. Be thoroughly familiar with a source before using it as a reference. There are standard abbreviations for most journals, but if you don't know it, spell them out and be consistent when abbreviating them. Usually, the standard format for a reference is author's last name, first and middle initials, title of the paper, journal of where the paper was published (in italics), year, volume (and number if necessary), page number (beginning to end). For example,

Nondek, L., D.R. Rodler, and J.W. Burks. 1992. Measurement of Sub-ppbv Concentrations of Aldehydes in a Forest Atmosphere Using a New HPLC Technique, Environ.Sci. and Technol. 26:1174-1178.

There are usually three ways to cite a paper: name and year; alphabet-number; and citation order. The choice is usually determined by the journal. The name and year system is simple such as "Nondek, Rodler, and Burks (1992)" or "Nondek et al. (1992)". The alphabet-number system is a citation by number from an alphabetized list of references. The citation-order system is a system of citing the references by number in the order that they appear in the paper.

How to Design Effective Tables and Figures

An effective way to present repetitive results is to use Tables and Figures. An effective table allows the reader to grasp the information clear enough to make the meaning of the results understandable without reference to a text. Tables should have relevant data and variables but not experimental conditions in the column. However, if an experimental condition (such as varying the temperature) is a variable in the experiment, it can have its own column. If experiments were performed at the same temperature, this information should be presented in the Materials and Methods or presented in the heading or footnote of the table. Table 1 is a good example of a complete table. The table lists the data that the researchers performed on red blood cells for a gene defect that causes a mutation in an enzyme, superoxide dismutase (SOD). The various mutants (columns 1 and 4), the number of subjects (column 2), and the enzyme activity (column 3) are clearly shown. Appropriate units of enzyme activity and statistical information are shown as footnotes. The control and the mutant enzyme activities are compared and therefore, the researchers have effectively shown that SOD activity is lower in the mutants than in the controls. This table contains no repetitive data nor experimental conditions in the columns.
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A table may be useful in presenting operating conditions in the Materials and Methods section for an instrument as illustrated in Table 2. This is effective because it is clearer to read from a table than from the text.
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A table may be useful for presenting properties for chemicals or reagents used in your experiment as shown in Table 3.
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Figures are used when clarity and conciseness are required and because certain types of data are more effective if they are presented in figures, such as graphs. For example, Figure 1 is an effective figure for the Results and Discussion section because the authors want to compare a field blank and an ambient air sample to convince the reader that any formaldehyde and acetaldehyde present in the air sample did not originate from the reagents or solvents used for the analysis.
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Figure 2 is effective for the Materials and Methods section because the authors want to describe a new gas chromatography set-up by a visual diagram rather than describe the intricate details in narrative form in the text.
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Figure 3 is effective because the authors want to propose a model based on their experimental results to understand the biogeochemical processes of chromium redox chemistry in flooded forest wetlands.
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Figures 4 and 5 are effective figures for the Materials and Methods section because flow diagrams of the two sample preparations for the analysis of PCDDs and PCDFs are easy to follow.
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Certain types of data are more effective if they are presented in figures, specifically graphs. Where possible, express data in narrative form in the text and minimize the use of figures and tables. However, if the data show pronounced trends, a graph may be more effective in presenting your results than a table. Figure 6 is an analytical calibration curve for cobalt and arsenic that was developed from helium inductively coupled plasma-mass spectrometry. Note how the axis and the figure captions are clearly and briefly stated. Make sure you properly label the ordinate and abscissa and that the ranges are appropriate for presentation.
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Finally, Figure 7 is an effective figure because the graph shows trends that are more obvious by visualizing rather than reading the text. Experimental data points as well as a theoretical transformation rates are well-defined and well-represented. Error bars are also revealed and all headings are appropriately labeled. Graphs, figures and tables must be neatly drawn. All figures must have the proper captions, headings, and a brief description of what information the figure is suppose to convey. Remember to always label your figures and tables, numerically (i.e., Table 1 or Figure 1) and always refer to the table or figure in the text of your paper, i.e., "The results of the transformation rates for ONP, 4-Me, and 4-Cl are shown in Figure 7."
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