Follow this PostLab guide for writing your lab report. A good strategy is to open a word processing file alongside this page and write the report following the directions step by step. Or you can print out all the instructions. Follow the LabWrite process, beginning with writing Methods and finishing with writing the title and references. Then when you've finished, you can rearrange the sections of your report in the proper order for turning it in.
1 Methods
Describing the lab procedure
Using your lab manual, handouts, and notes taken during the lab as a guide, describe in paragraph form the experimental procedure you followed. Be sure to include enough detail about the materials and methods you used so that someone else could repeat your procedure.
The Methods section is a concise chronological description of the laboratory procedure you used in the lab. It's important to remember that even though the teacher who reads your lab report already knows the lab procedure, you should write it as if he or she did not. The point is to demonstrate that you have a solid grasp of the procedure you followed. Describing it clearly and in detail allows the teacher to see that you understand the procedure.
- Begin by reviewing the directions in the lab manual and any notes you took as you did the lab. If it is a complex procedure, make a rough outline of what you did.
- Write the procedure in paragraph form. For relatively simple labs, one paragraph will do; more complex labs will take multiple paragraphs. Keep the paragraphs relatively short because it's hard for readers to process detailed information like this without sufficient breaks.
- Describe what you actually did in your own experiment, even though it may be somewhat different from the ideal procedure in the manual. The Methods section should be an accurate reflection of what you did.
- Avoid putting any results of the lab in the Methods. Just describe what you did, not what you found.
- Use the proper past tense and passive voice. Methods are usually written in past tense because you are describing what you have already done. They are also typically written in passive voice ("Two ml. were pipetted into a test tube"). However, your lab instructor may permit you to use active voice, which uses first person, "I" or"we" ("We pipetted 2 ml. of the solution into the test tube").
More helpful hints:
- To make your description of the experimental procedure clear, use appropriate transitional or "sign post" words that indicate a sequence and help the reader follow the sequence: step 1, step 2, step 3; first, then, finally; first, second, third; after, next, later, following; etc.
- Include the methods you used for both gathering data and analyzing the data.
For more advanced labs:
- If your lab is complicated, perhaps consisting of more than one experimental procedure, then consider dividing your Methods into sections with subheadings.
- If you used what is considered a standard procedure (one that competent scientists in the field are likely to be familiar with) then there is no need to describe it in detail. Simply state that you used that procedure, being sure to give its common name. (If you are not sure about what standard procedures are in your field, ask your lab instructor.)
- When describing an apparatus or instrument, it's better to include a sketch of it rather than to try to describe it fully in words. This is especially useful in cases where the apparatus is complex or designed by you. All you need is a couple of sentences that give a general sense of the apparatus, and then refer the reader to the figure that contains the sketch, the same way you would refer the reader to tables or graphs.
2 Results
Making sense of your data for yourself and others
Step 1: If you haven't already done so, put your lab data in visual form by creating appropriate tables, graphs, and other figures. Representing your data in a visual format will allow you to identify trends and relationships among variables more easily.
- Establish what types of data you have, quantitative or qualitative.
- Determine if the data should be represented as a table or a graph.
- If you decide to use a graph to represent your data, determine which type of graph is one that best represents your data.
- If a table is the best format for your data, then modify the table you used to collect your data so that it is labeled and organized properly. Go to Designing Tables for more help with tables.
Step 2: Once you have generated visual representations of your data, decide the order in which your tables, graphs, or other figures should be presented in the Results section.
The visuals tell the main story of your data, so you need to decide how to organize visuals so that they tell the story most effectively. Deciding what order to put your visuals in is more of an issue in complex labs with multiple data sets, and may not be an issue in simple labs. If you have been told what visuals to include in your report and the order to put them in, go to Step 3 of Results.
Three ways of organizing your visuals:
- chronological order: if the lab consists of more than one procedure, you can present the results in the order in which you did the procedures, especially if that order provides a useful way of leading the reader through the results.
- order of importance: arrange the visuals by putting the one that is the most important first and then the others in descending order of importance.
- order of generality: sometimes it is better to start with the most general representation of the data and then place the more specific ones after that, especially if the specific ones serve to support the broad representation or add more details to it.
Step 3: Review all the data from your experiment. In a sentence or two, summarize the main finding of this lab. This is the opening sentence(s) of the Results section.
Summarizing your overall results in a sentence or two allows you to make sense of the findings of the lab for yourself and for your reader. A one- to two-sentence summary allows the lab instructor to judge how well you understand the lab as a whole.
- Review the findings in your visuals (tables and graphs and other figures). If you have trouble shaping a one-sentence summary, look for a unifying feature among the data sets. This is likely to be the dependent variable. The sentence will be a general statement that summarizes your findings about that variable or related variables.
- You can start the sentence in several ways: "The results of the lab show that …"; "The data from the experiments demonstrate that…"; "The independent variable X increased as Y and Z were…."
Step 4: In separate paragraphs, summarize the finding in each of your visuals--tables, graphs, or other figures. First state the overall relationship or interaction among variables that each visual represents. Then include any specific details from the visual that are important for understanding the results. Refer to your tables, graphs, or other figures as figure or table 1, 2, 3, etc.
The main job of the Results section is to report data from the lab. The Results typically consists of both visual representations of data (tables and graphs and other figures) and written descriptions of the data.
Describe each visual in a separate paragraph. Each paragraph has two parts:
- The first sentence gives the general finding for the visual, what it indicates overall, and
- The following sentence(s) provides key details from the visual that are important to understanding the experiment (don't include all the details).
Refer to your visual(s) in the written part of your Results in one of two ways:
- Refer to your visual(s) at the beginning of your findings, for example, "Table 1 shows that the reaction times decreased as the strength of the solution increased." "Figure 3 demonstrates that the mortality rate among riparian mammals adhered to approximately seven-year cycles." (It is also possible to use verbs such as "lists," "displays," "describes," etc.)
- Refer to your visual(s) in parentheses at the end of the of your findings. For example, "The reaction times decreased as the strength of the solution increased (Table 1)." "The mortality rate among riparian mammals adhered to approximately seven-year cycles (see Figure 3)." (Ask your teacher which format to use for parenthetical documentation.)
Step 5: Complete the Results by placing all the elements you've written in the proper order: (1) the sentence summarizing the overall data for the lab; (2) the paragraphs of word descriptions for each visual arranged in the order the visuals are presented.
The Results looks like this:
Summary of overall findings of lab
Paragraph related to visual 1
- Sentence of overall finding from visual 1
- Sentence(s) with key details from the visual 1
Paragraph related to visual 2
- Sentence of overall finding from visual 2
- Sentence(s) with key details from the visual 2
Paragraph related to visual 3
- Sentence of overall finding from visual 3
- Sentence(s) with key details from the visual 3, etc.
3 Introduction
Establishing a context for the lab
Step 1: Revise your answer to PreLab question 1 in one or two paragraphs. Begin the Introduction with 1 or 2 sentences clearly stating what scientific concept the lab is about. Then use the rest of your answer to question 1 to complete the paragraph with information about the scientific concept. Revise your answer so that it includes only the information that relates specifically to this lab. If you have a lot of information, make two paragraphs. Note any citations you use here for including in the References section of your report.
- If you are having trouble writing a good opening sentence for the lab report, you can say something like: "This laboratory experiment focuses on X…"; "This laboratory experiment is about X…" ; "This lab is designed to help students learn about, observe, or investigate, X…." Or begin with a definition of the scientific concept: "X is a theory that…."
- Once you have your opening sentence, you are ready to complete the opening paragraph by telling what you know about the scientific concept. The point is to show your lab instructor that you have a good grasp of the scientific concept. Revise the rest of Question 1 by:
- Focusing it so that it contains information about the concept that is most clearly related to the lab procedure (not everything there is to know about the concept)
- Incorporating additional relevant information about the concept you may have learned since doing the PreLab.
- Changing it so that the scientific concept is appropriate to the lab (this would apply if all or parts of what you wrote about the scientific concept in the PreLab are wrong for this lab).
- If you have a lot to say about the scientific concept, use more than one paragraph.
- This part of the Introduction is typically written in present tense.
For more advanced labs:
If you are writing a lab report that is more like a full scientific paper, you may need to do more research using the Internet and library. With your teacher's guidance, you should search the recent scientific literature to find other research in this area of study. Summarize that research in a paragraph or so, stating what the general findings have been and using those findings to describe the current knowledge in the area (such a "review of the literature" is typical of scientific journal articles). This summary should come after your initial sentence about the scientific concept. For help with citing references, go to Citations and References.
Step 2: Revise your answers to PreLab questions 2 and 3. Write the main objectives of the lab in sentence form. Then complete the paragraph by describing how the achievement of these objectives helped you learn about the scientific concept of the lab.
- If your response to Question 2 was a list of objectives, revise it by summarizing the primary objectives in your own words. The point is to demonstrate your understanding of what you were supposed to do in the lab. With most labs, you should be able to do this in 1 or 2 sentences. You can begin by saying something like: "The main objectives of this lab were to…"; "In this lab we were asked to …." This will be the beginning of the paragraph.
- Continue the paragraph by revising your answer to question 3, showing that you comprehend the purpose of the lab. Revise your answer by making it clear how accomplishing the objectives of the lab helped you to learn about the scientific concept of the lab. You can start by saying something like this: "The objectives of this lab enabled me to learn about X by…"; "Performing these objectives helped me to understand X by…."
- This part of the Introduction is usually all in past tense.
- If you have redefined the scientific concept of the lab since the PreLab, revise your answer to question 3 accordingly.
Step 3: Revise your answers to PreLab questions 4 and 5 in a paragraph or two. First, state your hypothesis clearly (even if it was not supported by the data). Then rewrite the explanation for your hypothesis so that your reader understands how the reasoning behind your hypothesis is based on the scientific concept of the lab.
- Revise your original hypothesis from PreLab question 4 so that it is clear that it is a hypothesis: "The hypothesis for this lab was…"; "My hypothesis was…"; "We predicted that…"; "I hypothesized that…."
- Finish the paragraph by revising your response to PreLab question 5, explaining how you came to your hypothesis. As you are explaining the reasoning you used to come to your hypothesis, be sure to make a direct connection between the hypothesis and the scientific concept of the lab. Rewrite it so that your reader can clearly see how you used your understanding of the scientific concept of the lab to make a prediction about the outcome of the lab. Refer to what you said in the first paragraph of the Introduction.
- One way to make your explanation clear is to use words that show causal links: because, since, due to the fact that, as a result, therefore, consequently, etc. For example, Since X happens in order to maximize energy, we hypothesized that . . .
- If your explanation is relatively long, use more than one paragraph.
Step 1: Begin the Introduction with 1 or 2 sentences clearly stating what scientific concept the lab is about. Then finish the paragraph by writing down details about this concept relevant to the lab that you can find in the lab manual, textbook, class notes, handouts, etc . . . Revise your answer so that it includes only the information that relates specifically to this lab. If you have a lot of information, make two paragraphs. Note any citations you use here for including in the References section of your report.
- If you are having trouble writing a good opening sentence for the lab report, you can say something like: "This laboratory experiment focuses on X…"; "This laboratory experiment is about X…" ; "This lab is designed to help students learn about, observe, or investigate, X…." Or begin with a definition of the scientific concept: "X is a theory that…."
- Once you have your opening sentence, you are ready to complete the opening paragraph by telling what you know about the scientific concept. The point is to show your lab instructor that you have a good grasp of the scientific concept. Revise the rest of Question 1 by:
- Focusing it so that it contains information about the concept that is most clearly related to the lab procedure (not everything there is to know about the concept)
- Incorporating additional relevant information about the concept you may have learned since doing the PreLab.
- Changing it so that the scientific concept is appropriate to the lab (this would apply if all or parts of what you wrote about the scientific concept in the PreLab are wrong for this lab).
- If you have a lot to say about the scientific concept, use more than one paragraph.
- This part of the Introduction is typically written in present tense.
For more advanced labs:
If you are writing a lab report that is more like a full scientific paper, you may need to do more research using the Internet and library. With your teacher's guidance, you should search the recent scientific literature to find other research in this area of study. Summarize that research in a paragraph or so, stating what the general findings have been and using those findings to describe the current knowledge in the area (such a "review of the literature" is typical of scientific journal articles). This summary should come after your initial sentence about the scientific concept. For help with citing references, go to Citations and References.
Step 2: Write the main objectives of the lab--the specific actions you took in the lab, such as measure, analyze, test--in sentence form. Then complete the paragraph by describing how the achievement of these objectives helped you learn about the scientific concept of the lab.
- Objectives are typically actions you are being asked to perform for the lab. Often the objectives are listed in the lab manual. Writing the objectives of the lab in your own words demonstrates your understanding of what you were supposed to accomplish in the lab. With most labs, you should be able to do this in 1 or 2 sentences. You can begin by saying something like: "The main objectives of this lab were to…"; "In this lab we were asked to…." This will be the beginning of the paragraph.
- Continue the paragraph by addressing the purpose of the lab. This is where you make the all-important link between what you do in the lab (the objectives) and the purpose for doing the lab: to learn something about the scientific concept of the lab. Read over the objectives again. In what way do you think that doing the experiment, accomplishing the objectives, helped you learn about the scientific concept? You can start by saying something like this: "The objectives of this lab enabled me to learn about X by…"; "Performing these objectives helped me to understand X by…."
- This part of the Introduction is usually all in past tense.
Step 3: State your hypothesis, what you thought the outcome of the experiment would be before you did it. This will be the first sentence of the hypothesis paragraph. To write a scientific hypothesis, you first need to identify the independent and dependent variables in the experiment. Write or sketch your hypothesis, describing the relationship among the variables you listed.
- Write your hypothesis so that it is clear, such as: "The hypothesis for this lab was…"; "My hypothesis was…"; "We predicted that…"; "I hypothesized that…."
- Often hypotheses are stated in terms of variables, the elements that the experiment focuses on. Be sure to use your original hypothesis, what you thought the outcomes of the experiment before you performed the experiment.
- A variable is what is measured or manipulated in an experiment. Variables provide the means by which scientists structure their observations. Identifying the variables in an experiment provides a solid understanding of the experiment and what the key findings in the experiment are going to be.
- To identify the variables, read the lab procedure described in the lab manual. Determine what you will be measuring and what you will be manipulating for each measurement. The value(s) you are manipulating is called the independent variable (also known as the "manipulated variable") and the value(s) you are observing/recording is called the dependent variable (also known as the "response variable"). Write down the dependent and independent variables.
- In more advanced labs, you may have multiple variables, more than one independent and dependent variable.
Look back over all the stages of the experiment:
- How do these variables relate to each other?
- Are there more than one independent and/or dependent variable being recorded through the various stages of the experiment?
- How does the data being recorded in one stage help you in the proceeding stages?
- If there are more than one independent and dependent variable, which one(s) will be used to answer the question being asked in the lab? That is, which variables will be used to formulate your hypothesis?
Step 4: Continue the paragraph you began with a hypothesis by explaining how you used your understanding of the scientific concept of the lab to arrive at your hypothesis.
- As you are explaining the reasoning you used to come to your hypothesis, be sure to make a direct connection between the hypothesis and the scientific concept of the lab. Rewrite it so that your reader can clearly see how you used your understanding of the scientific concept of the lab to make a prediction about the outcome of the lab. Refer to what you said in the first paragraph of the Introduction.
- One way to make your explanation clear is to use words that show causal links: because, since, due to the fact that, as a result, therefore, consequently, etc. For example, Since X happens in order to maximize energy, we hypothesized that . . .
- If your explanation is relatively long, use more than one paragraph.
4 Discussion
Interpreting the results of the lab
Step 1: Write a sentence or two stating whether or not the results from the lab procedure fully support your hypothesis, do not support the hypothesis, or support the hypothesis but with certain exceptions.
Experimental science is all about testing hypotheses. Thus, the statement of whether or not your hypothesis has been supported is critically important to the lab report. It is by no means a failure if your data do not support your hypothesis; in fact, that can be more interesting than the other way around, because you may find a new perspective for looking at the data. Failure to support hypotheses is common in science, and often serves as a starting point for new experiments.
- Go back to the statement of hypothesis in the Introduction. Then review your findings, the data from the experiment. Make a judgment about whether or not the hypothesis has been supported. It is at this point that you, as a scientist, must be as unbiased and objective as possible.
- Write a statement stating your judgment. There are three possible judgments you can make:
- the data support the hypothesis;
- the data do not support the hypothesis; or
- the data generally support the hypothesis but with certain exceptions (tell what those exceptions are).
Example: "The hypothesis that X solution would increase in viscosity when solutions Y and Z were added was supported by the data."
Step 2: In a paragraph, identify specific data from your lab that led you to either support or reject your hypothesis. Refer to the visual representations of your data as evidence to back up your judgment about the hypothesis.
It is important to back up the statement about the hypothesis with direct evidence from the lab data that support, do not support, or partially support the hypothesis.
- Return to the Results to identify the particular data that led you to your judgment about the hypothesis.
- Write a paragraph (or 2 if necessary) in which you present the relevant pieces of data from the lab and show how they relate to the hypothesis.
- Refer to data from specific visuals appropriately: Table 1, Figure 2, etc.
Step 3: In a paragraph, use your understanding of the scientific concept of this lab to explain why the results did or did not support your hypothesis. If the hypothesis from the Introduction was not fully supported, show how your understanding of the scientific concept has changed. Note any citations you use here for including in the Reference section of your report.
In Step 2 you pointed to data that led you to your judgment about your hypothesis. Now you use your understanding of the scientific concept of the lab to explain your judgment. Whatever the relationship between the hypothesis and the results, you must provide a logical, scientific basis for it.
Return to the scientific reasoning you used to generate your hypothesis (at the end of the Introduction). Use it and your understanding of the scientific concept of the lab as starting points for your explanation. Your explanation is likely to follow one of four scenarios. Choose the one that best fits your report:
- If the results fully support your hypothesis and your reasoning in the Introduction were basically sound, then elaborate on your reasoning by showing how the science behind the experiment provides an explanation for the results.
- If the results fully support your hypothesis but your reasoning in Introduction was not completely sound, then explain why the initial reasoning was not correct and provide a better reasoning.
- If the results generally support the hypothesis but in a limited way, then describe those limitations (if you have not already done so) and use your reasoning as a basis for discussing why those limitations exist.
- If the results do not support your hypothesis, then explain why not; consider (1) problems with your understanding of the lab's scientific concept; (2) problems with your reasoning, and/or (3) problems with the laboratory procedure itself (if there are problems of reliability with the lab data or if you made any changes in the lab procedure, discuss these in detail, showing specifically how they could have affected the results and how the uncertainties could have been eliminated).
Step 4: Discuss other items as appropriate, such as (1) any problems that occurred or sources of uncertainty in your lab procedure that may account for any unexpected results; (2) how your findings compare to the findings of other students in the lab and an explanation for any differences; (3) suggestions for improving the lab.
After dealing with the critical issue of the hypothesis, the rest of the Discussion may consider other issues. You can address these in separate paragraphs.
- Return to the notes you took during the lab procedure. Look for possible sources of uncertainty in setting up the lab, calibrating instruments, and taking measurements as well as problems with materials you are using.
- In scientific articles, the Discussion is where scientists typically compare their results to those from other scientific experiments. You can do something similar by comparing your results to those of other students in the lab. In your paragraph, comment on any similarities or differences you find and offer possible explanations for the differences. Be sure to check with the lab instructor to see if it is permissible to compare results.
- Professors who write lab manuals are typically interested in how they can improve the experiments in the manuals. You can also demonstrate your ability to provide productive critique of the lab by offering suggestions for improvement.
For advanced labs:
- It may be useful to classify the kinds of uncertainty you have identified. Sources of uncertainty can be classified as random--those that cannot be predicted--or as systematic--those that are related to personal uncertainty, procedural uncertainty, or instrumental uncertainty.
5 Conclusion
Focusing on what you learned by doing the lab
Step 1: Write a paragraph summarizing what you have learned about the scientific concept of the lab from doing the lab. Back up your statement with details from your lab experience.
The Conclusion is where you make it clear to the lab instructor what you learned in the lab experience. Since the purpose of the lab is to learn something about science, take the time to write a Conclusion that convinces the lab instructor of what you have learned.
- Return to the scientific concept you established in the Introduction. But instead of describing what you know about the scientific concept in the Conclusion, describe what you learned about the concept from doing the lab. For example:
- How has your understanding of the concept improved or otherwise changed from doing the lab?
- What specific aspects of the procedure or data contributed to your learning?
- What difficulties did you have with the concept before doing the lab and how were those difficulties alleviated by doing the lab?
- How might what you have learned in the lab be applicable in the future?
- Be direct in your statement of what you have learned. Don't be afraid to start out saying, "In this lab, I learned that ...." This sort of clarity will be appreciated by the reader. Elaborate on your statement with additional details about what you have learned.
Example: "The hypothesis that X solution would increase in viscosity when solutions Y and Z were added was supported by the data."
Step 2: If there is anything else you have learned about from doing the lab, such as the lab procedures or kinds of analyses you used, describe it in a paragraph or 2.
It is important to back up the statement about the hypothesis with direct evidence from the lab data that support, do not support, or partially support the hypothesis.
- There may be more that you have learned about from the lab experience than the scientific concept of the lab. If so, write a paragraph describing it. For example:
- Was there anything in the lab procedure that you found particularly interesting to learn how to do?
- Did you apply a procedure for analyzing data that was useful to learn about?
- Did you learn anything about using a spreadsheet or graphing or creating other visuals?
- Did you learn anything about writing or about science from writing the report?
6 Abstract
Summarizing the lab report
Summarize each major section of the lab report--Introduction, Methods, Results, Discussion, and Conclusion--in 1 sentence each (two if a section is complex). Then string the summaries together in a block paragraph in the order the sections come in the final report.
You can think of the Abstract as a miniature version of the whole lab report. Read each section of the report and boil it down to a sentence. This means that you need to determine the most important information in each section.
- Here are some suggestions for what to include in each sentence of the Abstract:
- Introduction: main objective(s) of the lab; hypothesis
- Methods: a quick description of the procedure
- Results: statement of the overall findings
- Discussion: judgment about hypothesis; explanation for judgment
- Conclusion: what you learned about the scientific concept
- Put all these sentences together into one paragraph with the heading "Abstract."
7 Title
Capturing the essence of the report
Write a title that captures what is important about the lab, including the scientific concept the lab is about and variables involved, the procedure, or anything else that is important to understanding what this report is about.
You write the title after you have written the other parts of the report, because the title reduces the report down to its essence, and it's not until you finish writing the report that you are able to identify what that essence is. A good title very efficiently tells the reader what the report is about.
Hints:
- If you are having trouble writing a title, try this approach. List the keywords related to the report: the scientific concept of the lab, the kind of procedure you used, names of key materials, what you experimented on, etc. Then write a title that describes the lab using the most important of these keywords.
- A title should use the fewest possible words to adequately describe the content of the report.
- A title should be as specific as possible. Specify the primary focus of the experiment and procedures used, including the scientific names of chemicals, animals, etc.
- Do not write the title as a complete sentence, with a subject and a verb. Titles are labels, not sentences.
- Do not use catchy titles. This is not an English paper or an editorial.
- Find the right balance for the length of the title: not so short that it doesn't communicate what the report is about but not so long that it rambles on for more than a line.
8 References
Acknowledging sources of information
If it is appropriate for your lab report, put a References section at the end. List all the sources you referred to in writing the report, such as the lab manual, a textbook, a course packet, or scientific articles. Be sure to use the proper form of documentation for the scientific field you are working in (ask your lab instructor if you are not sure). See Citations and References
- Different scientific fields use somewhat different styles for documenting sources in the References. Check to see which style is appropriate for your class.
- You can find information about various documentation styles at Citations and References