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Understanding the Structure of the Lab Report

Most lab reports have eight basic elements: title, abstract, introduction, materials and methods, results, discussion, conclusion, and references. Some lab reports have additional elements, such as acknowledgments and appendixes. Although each researcher or instructor might prefer a slightly different format and style for organizing and presenting information, most lab reports follow a common structure reflecting the scientific method valued by scientists and engineers for centuries. This structure is typically used in lab reports that describe attempts to test a hypothesis or answer a question. It might also be used in lab reports that merely describe following a procedure and report the results of that procedure.

If you are a student, be sure to follow your instructor’s guidelines for the structure of your report. For example, some instructors prefer that you combine the results and discussion sections. For studies involving multiple procedures and generating large amounts of data, your instructor might prefer that you present one set of data and analyze it before you introduce the next set of data.

The following discussion focuses on writing lab reports for undergraduate science and engineering courses.

The title should be informative enough to enable readers to decide whether the report interests them. An informative title helps scientists and engineers save time by using abstracting and indexing services to locate the research most relevant for their needs.

Write your title with your readers in mind. Use only words and abbreviations that are familiar to them. The keywords in your title should be the terms commonly used by readers searching for information in your subject area. Keep in mind that because effective titles are specific, they tend to be long.

The abstract summarizes the entire report, mirroring its structure: introduction, methods, results, discussion, and conclusion. However, because of space limitations, each section is addressed in only a sentence or two. Because your abstract might be distributed more widely than your entire report, it should contain enough information so that your readers can quickly decide whether to locate and read the whole report. Readers of abstracts are most interested in what questions motivated your study (introduction), what answers you discovered (results), and what implications your findings have (conclusions). A well-written abstract can also meet readers’ need to stay up to date on research findings without spending a lot of time doing so.

Most readers prefer informative abstracts, which present the major findings. Less popular is the descriptive abstract, a shorter form that simply states the topics covered in the report without presenting the important results or conclusions.

The introduction is the section of the report in which you begin to establish that your work is important. Here, you place your work in the broader context of your field by describing the hypothesis or question your study attempted to address and why this question is significant. The introduction should include a concise review of previous research relevant to your study and should describe how your study extends the knowledge in your field or overcomes a weakness in previous studies. By placing your study in the context of previous research, you establish its significance. Provide just enough detail to help readers understand how your study contributes new information to the field and to communicate the purpose of your study.

If you think readers will need specialized knowledge or theoretical background to understand your study, define important terms and present theoretical concepts in this section. Use your understanding of your audience to help you determine how much theoretical background to include. Often, instructors will ask you to write for an audience of classmates who are familiar with the general subject area but not familiar with the specific lab work you are reporting.

Your introduction should also briefly describe your methods: what you did to find an answer to your research question. Although your methods section provides a detailed account of your approach, your introduction should persuade your readers that your methods are appropriate given what has been done in previous studies.

If you include equations in the introduction, adhere to the conventions presented in the Guidelines box.

Your purpose in writing the materials and methods section (sometimes called equipment and methods) is to convince your readers that your approach was appropriate for the question you hoped to answer, that you conducted your research or experiment carefully, and that your results are credible. Describe your methods in enough detail that another researcher could perform the same experiment using the same materials and methods. This characteristic, called replicability, is one of the foundations of the scientific method.

Most researchers begin the materials and methods section with a description or list of materials. Include any human subjects, organisms, chemicals, tools, and measuring devices used. Your description of materials might also include sketches, diagrams, schematics, or photographs of equipment, as well as explanations of how you set it up.

Next, describe your procedures. Include relevant conditions such as temperatures, observation dates and times, instrument settings and calibration, and site locations for field studies. Also indicate whether you encountered any difficulties with standard procedures and, if so, how you modified your approach to address those difficulties. Finally, if you had to make subjective decisions in collecting data, explain your choices. Although your audience might want to repeat your experiment, some instructors prefer that you avoid numbered, step-by-step instructions, presenting instead an organized description of what you did in sufficient detail that readers can understand your process. Organize this section chronologically, in the order in which you conducted your research or experiment. Include only those procedures that led to results that you present in the report.

When providing details, assume your readers are unfamiliar with the particulars of your experiment but know enough about lab procedures to evaluate your efforts. Your credibility rests on your ability to explain clearly what you did and why.

Although writing in the active voice (“I collected three soil samples”) is generally more concise, clearer, and more interesting than writing in the passive voice (“Three soil samples were collected”), the sciences and engineering have a long tradition of using the passive voice. The passive voice emphasizes the material studied and the actions taken, deemphasizing the role of the researcher. However, more and more scientific and engineering publications are accepting use of the active voice. Check with your instructor to learn which style he or she prefers.

Think of the results section as an opportunity to present the evidence you will use to support the claims you will make in your discussion. How persuasive this evidence is depends on how successfully you present it to your readers.

Your research will likely produce raw data in the form of numbers. In the results section, your task is to summarize the data relevant to the question or hypothesis you discussed in your introduction. Omit irrelevant data, but explain why you are doing so. When summarizing your data, help readers understand your findings by emphasizing major trends, magnitudes of values, associations, patterns of statistical significance, and exceptions. Typically, you present results in the same order used in describing the steps in the methods section, but you can change the order if you have a good reason to do so. For instance, you might use the more-important-to-less-important organizational pattern by beginning with the set of data that most clearly supports or negates your hypothesis.

Be sure your data are complete and organized. For each major trend or pattern, begin with a statement of your findings and then support your statement with data. Depending on the type of data, you might present your supporting evidence with a combination of text and graphics (such as tables, graphs, and diagrams). If you include graphics, refer to them in the text with a statement explaining their significance.

In the results section, do not interpret or explain your data and do not speculate about problematic or atypical data. Save those explanations for the next section, the discussion.

Sometimes called analysis, the discussion section is where you interpret your results: that is, you answer the question or support (or argue against) the hypothesis you discussed in your introduction.

In organizing the discussion section, start by presenting the most important findings, which might include major trends, magnitudes of values, associations, patterns of statistical significance, and exceptions. Focus on offering explanations for your findings. Support your argument with data from your results, and do not hesitate to discuss problematic data or “failed” experiments. Remember that sometimes a negative result or a failure to find a significant difference helps researchers create new knowledge in their field. If your results do not support your hypothesis, argue for rejecting your hypothesis. If appropriate, support your argument with references to the work of other researchers, describing the degree to which your results match the results of previous studies. If your findings do not match the results of previous studies, suggest possible explanations for the differences.

Summarize the main points covered by your report in one or two concise paragraphs. Begin by reviewing the purpose of your research or experiment and the hypothesis (or hypotheses) you tested. Next, summarize the most important implications of your findings. The conclusion is your final opportunity to persuade your audience of the significance of your work. Do not introduce any new information or analysis in this section.

If you received assistance from colleagues during the study or while preparing the lab report, identify and thank these people in an acknowledgments section. If your study was supported by funding, list the source of financial support in this section as well. Figure 19.1 shows a concise acknowledgments section. Typically, scientists and engineers ask permission of the people they wish to thank before including them in the acknowledgments.

List all the references you cited in your lab report. (Do not list any sources that you consulted but did not cite.) Most of your citations will appear in the introduction, materials and methods, and discussion sections. However, check the other sections as well to make sure you include all sources cited in your report. Most scientists and engineers follow a particular documentation system for their discipline (see Appendix, Part B). Check your instructor’s preferences before selecting a documentation system.

An appendix, which follows the references, is the appropriate place for information that readers do not need to understand the body of your lab report. For example, an appendix might include long tables of measurements, specialized data, logs, analyses, or calculations.

By following the basic structure of a lab report discussed here, you will help your readers manage the large quantities of information produced in science and engineering. The title and abstract will help readers quickly decide if a report is relevant. The introduction and conclusion will provide the context for the study and describe the most important results of the study. If readers are persuaded to read further, the methods, results, and discussion will provide the detailed information they seek.