In general, reports of student experiments should be written in the same style as research articles in the natural sciences (including experimental sciences). Indeed, this is the style best suited for reporting to others what experiments you conducted and what you learned as a result.
Having said that, the fields of physics, chemistry, Earth science, and biology all have long histories and have each evolved independent academic styles. Needless to say, fields of applied science such as medicine, engineering, agriculture, and pharmacology date back even farther than the natural sciences and have each developed their own ways of doing things. Consequently, the way in which you write your report will vary slightly from project to project; when preparing your report for a project, pay close attention to the description given for that project.
How to structure your report
Experimental reports (like research articles in experimental science) consist of the following sections.
- Objectives
- The principles underlying the experiment
- Experimental methods
- Results
- Discussion
Objectives
This section describes the knowledge you are hoping to gain from your experiment.
In a research article, this section would discuss previous research conducted within the field in question: how much was previously known, and what remains unknown? This would be followed by a discussion of any new hypotheses introduced in the paper and a description of the experiments conducted to test them.
In a student experiment report, the “hypotheses” that you set out to test experimentally are actually well-established scientific facts that have been thoroughly investigated previously; in conducting experiments that repeat these tests, your goal is to learn experimental techniques and data-processing methods and to study the hypothesis–experiment–assessment cycle that forms the heart of the scientific process. Thus, your Objectives section should include concise descriptions, based on textbook discussions and the actual experiment you conducted, of what you set out to investigate and what you hoped to learn through your experiment.
The principles underlying the experiment
Experiments are conducted with a grounding in some type of natural-science principles or theories. This section summarizes the principles and theories relevant to the natural phenomena on which your experiment is premised, including items such as measurement methods and operating principles of experimental instruments. Referring to textbooks, describe here the core principles that are more crucial for the execution of your experiment. When writing equations, make sure they are numbered.
Experimental methods
Depending on the project, this section may consist simply of an “Experiment” section, or may include a “Materials and Methods” discussion; in any case, this is the section in which you describe your experimental procedures and conditions in detail. In general, the most important point of this section is to tell the reader everything necessary to reproduce your experiment. The important question to answer is precisely what experiment did you actually conduct? Your lab notebook will play a decisive role here.
Although detailed discussions of experimental techniques may be found in textbooks, the “Experimental Methods” section of your lab report will differ from these. Textbooks are written for people conducting experiments for the first time and must include details such as cautionary notes regarding the handling of instruments and tools. This content is not necessary in your report. Moreover, there may be cases in which the actual procedure you followed differed from that described in the textbook. For these reasons, copying textbook content verbatim into your report is considered cheating, and in some cases may be treated as the equivalent of lying.
Your report should provide a concise summary—based on the notes you took in your lab notebook—of the actual experimental procedures you executed, as well as a discussion of any experimental factors not cited in textbooks that could have affected your experimental results.
Results
This section is an objective report of your experimental results. Some students mistakenly believe that the actual numerical data, charts, photographs, and sketches obtained by the completion of the experiment constitute the actual “results,” but this is incorrect. Instead, the role of this section is to present your results in a way that clearly indicates how they relate to your actual experimental procedures: what phenomena transpired due to what procedures you executed, what values did you obtain upon taking what measurements, etc. For this reason, the notes you record in your lab notebook will be crucial for preparing this section: you will only be able to provide the reader with a good description of your results if you are meticulous about noting everything you observe during your experiment.
If the results obtained from your experiment are numerical data, present them in the form of tables or graphs to ensure that they are easily understood. It is very important to note the units and the significance of numerical values. In your data-processing work, be careful to account properly for the number of significant digits in your raw measured data. As for the proper creation of graphs, please refer to the specific guidelines we have presented for this task elsewhere in this documentation: How to make graphs. All figures and tables should be numbered and given titles. In addition to graphs, your report may contain other figures, including instrument diagrams, experimental procedure flowcharts, chromatograph charts, photographs, and sketches. These figures should all be numbered (Figure 1, Figure 2, etc.), and the main text should refer to figures by number. Tables are numbered separately from figures (Table 1, Table 2, etc.).
Even results that are not numerical data—such as descriptions of phenomena or reports of observations—should be described objectively and in easily-understood ways that clearly establish their relationship to the steps you took.
Discussion
Many authors worry about what content to include in this section.
In a scientific article, the role of this section is to offer appropriate interpretation of data obtained as the results of experiments, to discuss whether or not the conclusions drawn from these results support the initially-stated hypotheses, to assess whether the plan of the experiment was successful, and to evaluate whether the experiment achieved its stated goals.
For student experiments as well, the goal is for students to experience this hypothesis–experiment–assessment methodology for experimental science, and thus in this section of your report, you will proceed as follows:
- 1.Interpret your experimental data and explain its significance.
- 2.Discuss the conclusions that follow logically from your findings.
- 3.Assess whether or not these conclusions achieve the originally-stated objective of the experiment.
Think carefully about experimental precision and experimental error
In experiments in which data are obtained in the form of numerical values, analyzing your data and understanding your experimental precision and experimental errors must be a central component of your thinking.
There is no scenario in which your experiment will yield values in perfect agreement with theory. This is because experimental measurements always include errors arising from instruments, experimental methods, and other sources. Indeed, the theoretical values may contain errors themselves. The extent of the conclusions derived from experimental data varies with the extent of the errors in the data. In general, the better the precision of your data, the more far-reaching the conclusions you can draw and the stronger the evidence you will have to confirm them. In the case of student experiments, the situation is somewhat reversed: the extents of the “hypotheses” you are attempting to verify are already well known, and you should think about experimental errors by asking whether the precision of your data is commensurate with these extents.
If your experiment finds a result that differs from a theoretical prediction, and you conclude solely on this basis that the experiment “failed,” then this is tantamount to a confession that you do not understand the concepts of experimental precision and experimental error. You must acquire a thorough understanding of your experimental apparatus—including questions such as which experimental steps contribute how much to the experimental error? and what is the precision of my measurement instruments?—and you must have a clear grasp of the extent to which the values you obtain are reliable. Then, taking full account of the trustworthiness of your experimental data, you must determine whether the data are consistent with your “hypotheses,” or whether they are at odds with your hypotheses. Only in the latter case can you conclude that fundamental flaws exist somewhere in your experiment. There are also cases in which, although your experimental data are not inconsistent with the “hypotheses,” you have still not achieved the level of reliability expected for your experimental method. In this case as well, you must search for the underlying cause somewhere within your experiment. If you can understand these factors—and especially if you can think of ways to improve the trustworthiness of your experimental data—then you will be in a position to prepare an excellent report of your experiment.
Even in cases where the output of your experiment is not numerical data, it is still important to think about the quality of your experimental results. This is not simply a matter of concluding that the experiment went well or the experiment did not go well; instead, you must reason logically to deduce which portions of the experiment made which contributions to the difficulties you encountered—and think about ways to improve those factors.
Question the limits of what your experiment can test
The question of how to design an experiment to test a given hypothesis—that is, experimental planning—is an important component of a typical scientific article. However, for student experiments, the experimental plans have already been well thought out, and there is essentially no room for improvement left to be considered regarding their effectiveness.
Still, because experiments must be completed within a fixed period of time, any actual experiment is limited to providing partial supporting evidence in favor of the natural laws in question, and can never be regarded as establishing definitive “proof.” In this type of experiment, the questions of (a) precisely how much was clearly established by the experiment conducted, and (b) what other investigations could be carried out to provide further supporting evidence (which experiments to perform and to what precision those experiments should be conducted) can provide excellent fodder for thought and discussion.
It is difficult to offer meaningful discussion of the correctness of your working hypotheses
As noted above, the “hypotheses” tested by student experiments are in fact established facts for which plenty of supporting evidence has already been accumulated, so there is not much leeway to consider the possibility that these hypotheses may be incorrect. (This is perhaps one reason for the difficulty of writing the Discussion section of your report.) Nonetheless, in cases where your experiment produced clear results in accordance with expectations, it is still meaningful to write statements along the lines of from result XX, we see clearly that YY is true. Such statements communicate that you clearly understood the relationship between the objectives of the experiment and your results. (Indeed, this is really all they can communicate.)
Answer the questions in the textbook
Most projects supply questions in the form of problems and points to consider that you should complete. Among these, the questions in the Results section are intended to make you focus on your experimental results; most of these are probably treated as questions for Discussion. At the very least, we ask you to answer these questions, but their real purpose is to get you thinking about some important considerations as you complete your experiment. Our hope is that, by pondering these questions while considering how they relate to the objectives of your experiment, you will ultimately be able to think about them in depth, beyond simply supplying answers.
Separate facts from inferences and clearly delineate quotes
A common problem we have noticed in reading various student reports is a tendency to intermingle inferences with objectively clear facts. To distinguish the two, the style of writing you use when stating objectively clear facts must differ noticeably from the style of writing you use when stating deductions drawn from those facts.
Another common mistake is to write statements in your report that cannot be tested by the experiment you conducted as if they were facts established by your experiment. Most of these are statements quoted from descriptions in textbooks or other reference material; in such cases, you must clearly indicate that the statement is a quote, and you must note the original reference in which you found it. Copying content without properly citing its source is plagiarism.
Finally, it is hopefully unnecessary to discuss all over again the issues of copying-and-pasting and verbatim replication; let’s all agree not to submit reports with copy-and-pasted or verbatim-replicated content. There is nothing to be gained by doing this. You may be thinking Oh, I’ll never get caught, but hear this: You will get caught, every time, without fail. Even if nobody says anything about it to you, this is not because you didn’t get caught; rather, it’s because the instructors were thinking rather than wasting time on students who can’t be bothered to study, I will ignore them and instead devote my full time and attention to students who are motivated to learn.
Note that we are not saying don’t discuss with other students, nor are we saying don’t look at past reports. Indeed, it is crucially important to look at a wide variety of materials and discuss thoroughly with others. However, the final report that you write and submit must be the product of your own mind and your own hands. Surely this is how you want it to be too!