Descriptive Labs SelfGuide

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PostLab: writing your lab report

SECTION ONE : Methods

Describing the lab procedure

Using your lab manual, handouts, and notes taken during the lab as a guide, describe in paragraph form how you did the lab. The point is to demonstrate that you have a solid grasp of the lab procedures, such as conducting a dissection or using specific laboratory equipment to determine an unknown. Provide enough detail of the materials you used and the methods you followed so that someone else could repeat the procedure. Make sure to note any differences between the procedures presented in the lab manual and what you actually did. This will be very important when you are writing the discussion portion of your report. Remember that the Methods should only describe what you did in the lab and not what you found.

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.

SECTION TWO : Results

Making sense of your findings for yourself and others

Step 1: If you haven't already done so, create appropriate tables, graphs, and other figures to enable you to visualize your lab data. Use a spreadsheet program or table function in a word processing program. If your lab data consists of only drawings, or observations, you may want to organize these in tabular format as well. If not, go to Step 2. Remember that representing your data in a visual format will allow you to identify trends, relationships, and other patterns in your data more easily.

Establish what types of data you have, quantitative or qualitative (refer to the Resources page in the web version of this document; once there, choose "Data Types").
Determine if the data should be represented as a table or a graph (refer to the Resources page in the web version of this document; once there, choose "Tables vs. Graphs").
If you decide to use a graph to represent your data, determine which type of graph is one that best represents your data (refer to the Resources page in the web version of this document; once there, choose "Graph Types").
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 (for help in making tables, refer to the Resources page in the web version of this document; once there, choose "Designing Tables").
If you need help creating a spreadsheet to make a table or graph, refer to the Resources page in the web version of this document. Once there, choose "Excel Tutorial."

Step 2: Once you have generated visual representations of your data, determine the best order for presenting the visuals. If the the proper order for visuals is already determined by the lab manual, go to step three.

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.

Review the findings in your visuals (tables, graphs, drawings, and other figures). If you have trouble shaping a one or two 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 The observations show that....

Step 4: In separate paragraphs, summarize the general finding in each of your visuals--tables, graphs, drawings, or other figures. First, describe any relationship or interaction which exists among variables for each visual. Then include any specific details from the visual(s) that are important for understanding the results. Refer to your tables, graphs, drawings, or other figures as figure or table 1, 2, 3, etc.

Describe each visual in a separate paragraph. Each paragraph has two parts:
1. The first sentence gives the general finding (see below for definition) for the visual, what it indicates overall, and
2. The following sentence(s) provides key details from the visual that are important to understanding the experiment (don't include all the details).
You can determine the general finding for each visual in one of two different ways:
1. as a summary of all the information in the visual OR
2. as a statement that focuses on the most important point that is made in the visual (important, that is, in terms of the hypothesis).
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 the percent yield of acetylsalicylic acid, commonly known as aspirin, from salicylic acid and acetic anhydride." (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.)

General Finding:

You can determine the general finding for each visual in one of two different ways:
1. as a summary of all the information in the visual OR
2. as a statement that focuses on the most important point that is made in the visual (important, that is, in terms of the hypothesis).

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. Remember that the Results only reports and describes what you observed and collected during your lab. The Results does not explain, discuss, or draw conclusions.

Summary of overall findings of lab
Paragraph related to visual 1
1. Sentence of overall finding from visual 1
2. Sentence(s) with key details from the visual 1
Paragraph related to visual 2
1. Sentence of overall finding from visual 2
2. Sentence(s) with key details from the visual 2
Paragraph related to visual 3
1. Sentence of overall finding from visual 3
2. Sentence(s) with key details from visual 3, etc.

SECTION THREE : Introduction

Establishing a context for the lab

Step 1: Begin the opening paragraph of the Introduction by stating the scientific concept (principle, theory, law) or laboratory procedure of the lab. Then finish the paragraph by writing down all the details about the concept or procedure relevant to the lab that you can find in the lab manual, textbook, class notes, handouts, etc. If you completed the PreLab, this step corresponds to
question 1. Note any citations you use here for including in the References section of your report.

Step 2: Write in sentence form the objectives for this lab--specific things you are being asked to do in the lab, such as measure, analyze, observe, test something, etc. Then, continue the paragraph by describing the purpose of the lab--how the achievement of these objectives are designed to help you learn about the scientific concept or procedure of the lab. If you completed the PreLab, this step corresponds to questions 2 and 3.

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. If your response to PreLab question 2 was a list of objectives, revise it by summarizing the primary objectives in your own words.
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 or procedure 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…." If you completed the PreLab, revise question 3, showing that you comprehend the purpose of the lab.
This part of the Introduction is usually all in past tense.

Step 3: Describe the questions you had before doing the lab, things you didn't understand or would like to know more about. These are questions about the scientific concept, lab materials, procedures, or application of this lab to other scenarios. If other questions came up as you were completing the lab, include them here as well. State why these questions are important to understanding the lab. Make sure to describe your questions in the context of the scientific concept for the lab. If you completed the PreLab, this step corresponds to question 4.

Since the purpose of the lab and the report is to help you learn something about science, the final paragraph of the Introduction should create a learning context for the rest of the lab report. Writing a paragraph that describes issues that you didn’t understand or wanted to know more about before or during the lab establishes a basis for learning. It shows what you may be able to learn by doing the lab. You will return to these issues in the Discussion.
If you did not do the PreLab, one strategy for finding these issues at this point is to go back to the lab manual and read the section about this lab. Look for things that you were unclear about before you did the lab. Perhaps, you didn’t fully understand aspects of the scientific concept for the lab. Or perhaps there were some details about how to perform the lab procedure that were not clear to you. It may be that you were curious about how you could apply the lab protocol to another situation. You can include issues that you still don’t understand.
To write the paragraph, describe what you don’t know or are just curious about. You can do this in sentence form or list them in bullets.
To show how the issues you raise are important to the lab, show how they relate to the main scientific concept or procedure of the lab.

SECTION FOUR: Discussion

Interpreting the results of the lab

Step 1: For the opening paragraph of the Discussion, explain what the findings mean in terms of the scientific concept or laboratory procedure of the lab. In other words, discuss the connection between the evidence you collected and what you were supposed to be learning about by doing the lab. If necessary, refer to graphs, drawings, tables, lists, or other visuals from the Results to support your explanation.

Go back to the first part of your Introduction where you establish the main focus of the lab--the scientific concept or procedure of the lab--and use what you have written to address the following questions in your opening paragraph of the Discussion:
- What is the connection between your findings and the scientific concept or procedure of the lab?
- What implications do the findings suggest about the concept or procedure?
- How do the findings relate to your description of what you already knew about the concept or procedure in the first paragraph of the Introduction?
If appropriate, refer to specific drawings, tables, or other visuals from the Results to support your explanation.

Step 2: Go back to the questions you raised in your Introduction, and in a paragraph or so, discuss any answers you arrived at as a result of doing the lab or as a result of additional research you may have done. Where appropriate, refer to specific data in your findings or to specific points in the protocol to support the answers to these questions. Finally, discuss the importance of these questions to the scientific concept or lab procedure you explored in this lab. Note any citations you use here for including in the References section of your report.

Return to the Introduction and to the original PreLab question (if you did one) where you raised the questions to guide your learning. Identify any of those questions that doing the lab or doing additional research provided answers for, even partial answers. These are the ones you can discuss in this section of the report.
In the Discussion, consider each question separately, unless some questions are better grouped together. Restate the question or issue and then present what you think is an answer to it. Then explain how you came to the answer. This is where you should refer to specific findings or other observations from the laboratory procedure.
If you are not sure of an answer, put in any qualifiers you think are appropriate. You can say that you think the answer is tentative.
For help with citing references, go to Citations and References in the LabWrite Resources homepage.

Step 3: In the final part of your Discussion, write about other items as appropriate, such as (1) questions from the Introduction that remain unanswered; (2) sources of uncertainty (see below for definition) in your lab methods that may have led you to unclear answers; (3) how your findings compare to the findings of other students in the lab and an explanation for any differences; (4) what further investigations you would do in order to gather more information; (5) suggestions for improving the lab.

SECTION FIVE: Conclusion

Focusing on what you learned by doing the lab

Step 1: Write a paragraph summarizing what you have learned about the scientific concept or procedure of the lab. Back up your statement with details from your lab experience.

Return to the scientific concept or lab procedure you established as your focus in the Introduction. But instead of describing what you know about it in the Conclusion, describe what you learned about it from doing the lab. For example:
- How has your understanding of ir improved or otherwise changed from doing the lab?
- What specific aspects of the lab experience contributed to your learning?
- What difficulties did you have with lab before doing it, 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.

Step 2: There may be more that you have learned about from the lab experience that is not directly related to the main focus of the lab, the scientific concept or lab procedure. If so, describe it in a paragraph or two.

Here are some examples of other things you may have learned by doing the lab:
- 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 how science works from writing the report?

SECTION SIX: 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 paragraph in the order the sections come in the final report.

Here are some suggestions for what to include in each sentence of the Abstract:
- Introduction: the main focus of the lab (scientific concept or lab procedure) and main objective(s) of the lab
- Methods: a quick description of the how the lab was done
- Results: statement of the overall findings
- Discussion: statement explaining the findings of the lab and their relationship to the scientific concept or lab procedure
- Conclusion: what you learned about the scientific concept or lab procedure
Put all these sentences together into one paragraph with the heading Abstract.

SECTION SEVEN: Title

Capturing the essence of the report

A good title very efficiently tells the reader what the report is about. Write a title that captures what is important about the lab, including the scientific concept the lab.

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 observed, etc.

Then write a title that describes the lab using the most important of these keywords.

Here are some other tips on creating a good title:

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.

SECTION EIGHT: References

Acknowledging sources of information

List all the sources you referred to in writing the report, such as the lab manual, a textbook, a course packet, or a scientific article. Be sure to use the proper form of documentation for the scientific field you are working in (see Citations and References in the LabWrite Resources homepage).

Different scientific fields use somewhat different styles for documenting sources in the References. For example, in chemistry you would follow the American Chemical Society (ACS) style. In biology, it would be the Council of Biological Editors (CBE) style. Check to see which style is appropriate for your class.
You can find information about various documentation styles at Citations and References.

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