PostLab: writing your
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
- 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,
- Include the methods you used for both gathering data and analyzing
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.
For help with creating visuals for lab report, follow these steps:
- 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.
The visuals tell the main story of your data. In relatively simple
labs, determining the order of the visuals may not be an issue because
you may have only one or two data sets to report. But in more complex
labs, ordering your data is an issue. Here are some suggestions for
ordering multiple data sets so that they make sense to the reader:
- 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
- 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- or 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, 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.
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
- The first sentence gives the general
finding (see below for definition) for the visual, what it indicates
- 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
- as a summary of all the information in the visual OR
- 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
You can determine the general finding for each visual in one of two
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.
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 visual 3, etc.
SECTION THREE : Introduction
Establishing a context for the lab
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.
- 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
" ; "This lab is designed to help students learn
about, observe, or investigate, X
." Or if you are working
with a scientific concept or procedure, you can begin by defining
it: "X is a theory that
"; or "X is a procedure
that is used for..."
- Once you have your opening sentence, you are ready to complete the
opening paragraph by telling what you know about the scientific concept
or lab procedure. The point is to show your lab instructor that you
have a good grasp of the scientific concept. Make sure to include
- Information about the scienctific concept or laboratory procedure
that is directly related to the lab (not everything there is to
know about the concept or procedure)
- Additional relevant information about the concept or procedure
you may have learned since doing the PreLab or since doing the
- If you have a lot to say about the scientific concept or lab procedure,
use more than one paragraph.
- This part of the Introduction is typically written in present tense.
- For help with citing references, go to Citations
and References in the LabWrite Resources homepage.
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 in the LabWrite Resources homepage.
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
- 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
- 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
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.
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
- 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
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
- How do the findings relate to your description of what you already
knew about the concept or procedure in the first paragraph of the
- 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.
In the final part of your Discussion, write about other items as appropriate,
such as (1) questions from the Introduction that remain unanswered; (2)
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.
- The final part of your Discussion allows you to bring up other issues
that may be appropriate for this lab. The list here is intended to
be suggestive. They point to the kinds of things you could address
- Previously, you had identified questions from the Introduction that
you could answer based on the lab research. Go back to the ones that
you don’t have a satisfactory answer for. Restate those questions
and talk about why they remain unanswered and speculate, if you can,
on what it would take to answer them.
- If you have reason to be uncertain about some of your data (for
example, it doesn’t match you think you should have found or
if you had problems in your lab procedure) go back to the notes you
took as you were setting up the lab and collecting and recording data.
These notes might enable you to identify sources
- In scientific articles, the Discussion is where scientists typically
compare their results to those from other scientific experiments.
If your teacher says it is permissible, 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.
- 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.
- In the Discussion section, use the past tense when referring to
what has been done in the experiment, but use present tense when talking
about most everything else, such as scientific concepts, explanations,
and references to articles. For help with citing references, go to
Citations and References
in the LabWrite Resources homepage.
Sources of Uncertainty:
In science, a source of uncertainty is anything that occurs in the
laboratory that could lead to uncertainty in your results. Sources of
uncertainty can occur at any point in the lab, from setting up the lab
to analyzing data, and they can vary from lab to lab. This is why it
is so important to keep detailed notes of everything you do in the lab
procedure and any problems you encounter. Try to be especially aware
of any problems in setting up the lab, calibrating instruments, and
taking measurements as well as problems with the materials you are using.
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.
SECTION FIVE: Conclusion
Focusing on what you learned by doing the lab
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
- 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
- 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.
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
- 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
- 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
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.
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