Laboratory Reports
Introduction to lab reports
Your written work in this course will consist primarily of laboratory reports. The purpose of the
laboratory report is to describe why you did the experiment, what you did, what results you obtained,
and what you think the results mean.
For this class, the laboratory report should not exceed 5 pages in length. The report should include at
least these four sections: Introduction, Methods, Results and Discussion. It is not necessary to use APA
format. The most important parts of the laboratory report are the methods and results sections. The
methods section should contain enough information so that another scientist can replicate your
experiment. The results section should summarize what happened in an honest manner. More
information about each section is given below. Here, we describe the report as if you were writing a full,
journal-style paper. However, your lab reports will be shorter and can omit sections if need be.
Title/Author
The paper should start with the title of the report and your name, each on a centered line.
Abstract
If you include an abstract, this should come next. In a journal submission, this is typically on a separate
page. If you include an abstract, either give it a title (“Abstract”), or give it narrower margins than the
running text to make it clear that it is the abstract. The abstract should be a short (100-200 words)
summary of the report. Write this bit last. The abstract should contain a single sentence describing the
problem, a short description of the approach you took (the logical structure of the experiment), and the
hypotheses you tested. Major findings should also be reported in summary form (significant or nonsignificant findings), as well as the conclusions that you draw from the results. A good abstract will
inform the reader of the contents of the report in enough detail to identify whether it is relevant to their
literature search, in as few words as possible. Beautifully written, flowing prose does not belong here.
Introduction
The purpose of the introduction is to get the reader interested enough to read the rest of the report. Thus
you should explain why you did the experiment. What question were you interested in answering?
What experimental strategy did you take? You may choose to include a summary of what you found out
from the experiment, or you may decide you would like to keep the reader in suspense. In a published
paper the introduction might include a summary of previous work by other scientists, but that is not
required for this course. The introduction should lay out the logical framework of the study, including
what you plan to manipulate and measure, and what you hope to achieve from this. If you haven’t
already done so, you should conclude with a clear statement of the hypotheses being tested.
Methods
The methods section should be written so that another scientist can replicate your experiment. What
were the stimuli? What apparatus was used to present the stimuli? What was the experimental
procedure? What was the observer’s task? What information was recorded? In this section, you do not
have to justify why you did what you did (although you may if you wish). Rather, just make sure we
can figure out what you did.
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Methods sections should be written clearly, and all pertinent details should be included. A good test of a
methods section would be to hand the paper to a colleague who has no prior exposure to your
experiment, and ask them to describe, in detail, how the experiment was carried out. If their description
is in agreement with your experience, then you know you have the words right.
Typically, a methods section is broken down into a number of subsections. These may include stimuli,
apparatus, design, procedure and observers, and many other important pieces of information, such as
how the monitor was calibrated, how participants were recruited and selected, etc. In our lab reports, we
are going to follow the example of visual psychophysics and include sections for stimuli, procedure and
observers. We generally don’t use much in the way of apparatus, so that information can be included in
with the stimuli. We don’t have anything against experimental design either, but our experiments will
tend to be simple designs, where one observer carries out all conditions, rather than the more complex
multi-group designs of cognitive and social psychology.
Stimuli
First of all you want to describe the basic form of the stimulus. A figure here may help to illustrate the
visual stimuli, and this is a good place to put it, if it wasn’t already covered in the Introduction. Identify
those parts of the stimulus that can change from trial to trial, and report which values were used.
Describe the equipment, stimulus size, duration, and all other details (see the handout “Specifying the
Visual Stimulus”).
Procedure
This is generally the toughest part, and it helps to break it down into short paragraphs. If applicable, start
by identifying the psychophysical method you used (e.g. method of adjustment, method of limits, etc.).
Next, you should describe events within a trial. More specifically, what happened, in what order, for
how long (or whatever the relevant factors are), and what was the observer’s task? Be sure to let the
reader know what information was recorded. In other words, what was the dependent variable?
Next, you should explain how the trials were put together. Often this is done in ‘blocks’ of trials for
longer experiments. What were the differences between the trials, and what was done to the stimulus? In
other words, describe the independent variable(s). It’s also nice to let people know how long each of
these ‘blocks’ of trials lasted.
Finally, how were the different blocks of trials put together across the experiment? Again, this is another
opportunity to divulge the independent variable or experimental manipulation, if you haven’t already
done so.
Observers
Here you describe the participants. There’s so much you could say, but much of it is irrelevant.
Typically, you could make do with the following: how many observers? Were they the authors of the
report, other vision researchers / graduate students, or were they naive as to the purpose of the
experiment? How was their vision (normal, or corrected-to-normal)? It is also customary to mention if
observers were paid. In some cases, it’s also important to describe how the observers were recruited,
especially if they represent a specific target population (e.g. the elderly), or you wish to generalize the
results.
Also, you should never refer to an observer (other than yourself) by name. One of the requirements of
Internal Review Boards (IRB’s) and funding agencies is concerned with the protection of participants’
anonymity. If you need to identify different observers, use a two- or three- letter code name. In vision
research, though, it is customary to use the observers’ initials, with their permission of course.
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The suggestions above are not exclusive. There are many excellent papers that might seem to ‘break the
rules’ listed above, or include other things I haven’t mentioned. If in doubt, include the information, and
let the readers sort out what’s relevant and what isn’t. The major criteria are to adequately describe the
stimuli, task, measurements/dependent variables, and the independent variables and their levels.
Results
What were the results? This section should let us know what happened, including the results of any
statistical tests. Graphs are highly recommended. Try to graph the data in such a way as to clarify for
the reader the features of the data you think are most important. In addition to providing summary
measures (such as the mean), provide some measure of the variability of the data (typically in the form
of error bars derived from the standard error of the mean). You may also wish to include tables of the
data or statistical analyses. You also need to include a written description of the results as they appear
on the figure. You should also discuss what you think the data mean.
In general, a results section will contain the data, including a description of the major findings, and any
trends observed. Raw data is often clumsy and boring, and most authors (and readers) prefer the data to
be summarized in the Results section. First of all, you need to explain what is being presented (means,
thresholds, difference scores, etc.), and how they were obtained from the raw data. It’s okay to tell the
reader that the data are means and assume they know what a mean is, but you should include things such
as how the data are grouped, how many observations are included in each mean, whether data are
averaged across observers, and the like.
There are two broad classes of statistics: descriptive statistics and inferential statistics. Descriptive
statistics are a way to summarize data, and these include averages (mean, median & mode), range,
standard deviation, standard error (often used in error bars) and so on. You should describe the data in
terms of central tendency (average), and dispersion (range, standard deviation etc.). Never assume that
the reader will bother looking at your beautiful figures unless you refer to them in the text, and point out
the key features you want the reader to observe (“Weber fraction increases as a linear function of the
weight of the standard”, for example). A general rule of thumb is to read your paper without including
the figures, and see is you are still able to get the main points across.
Inferential statistics are calculated measures such as t-scores or F-statistics that allow us to compare the
data with established probability distributions or tables in order to test hypotheses. The statistical test
you use will depend on the hypothesis and the type and organization of the data, but there is a general
form for the results of tests. For example: “Müller-Lyer comparison stimuli were judged as significantly
shorter than the standard length (t=5.68, df=9, p<.01, one-tailed test).” For an ANOVA, the
corresponding statement would be something like “There was a significant effect of stimulus type
(F(1,59)=17.24, p<.05) and set size (F(3,59)=19.56, p<.01), but there was no significant interaction
(F(3,59)=1.96, NS).”
Discussion
In the results section, you described the data, and included the results of the statistical tests without
judgment or commentary. In the discussion, you get to interpret your findings. Don’t simply restate the
results, but relate the results to the hypotheses stated in the Introduction. Explain what implications
these results have for the theory you may have proposed earlier, or other people’s theories. Did the
results answer the question you set out to answer? (If the results are ambiguous and do not allow you to
draw any firm conclusions, state this rather than trying to “get the right result”. In this course, we will
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not penalize very much if your experiment did not “work”, as long as your basic design was sensible
and your report clear.) You can also use the discussion section to revisit the logical framework in the
Introduction, and modify or extend it. A lot of the time you will be able to suggest further areas of study
which might help enlighten a particular problem you have identified, or simply identify questions which
need to be answered. If you think of problems or shortcomings in your study, feel free to critique your
own work here. We do this all the time in science, mostly because otherwise someone else will do it for
you, and make you look like you hadn’t thought of it first. Once again, there aren’t any specific rules for
a discussion, just an opportunity to continue the discourse you started in the Introduction, but in light of
the new results you obtained.
References
Every time you report someone else’s work, you give them credit in the text by referencing the
author(s) and the year of publication (e.g., Campbell & Robson, 1968). In the reference list, you give the
full description of each source you cited, listed alphabetically by author. It looks nicest if you start each
line without an indent, but indent subsequent lines of references longer than one line. Single-space
individual references, but leave a blank line between each reference. See earlier handouts for examples.
If you don’t have any references, you will omit this section.
Table Captions / Figure Captions
These have a section of their very own. List them in order, all the table captions first, then all the
figure captions. See the handout on graphs for how to write captions.
Tables and figures and their captions
In a typical journal submission, the references section is followed by a section giving the figure and
table captions (each in order by number). Then, the tables and figures go at the very end, in the same
order as the captions. Nothing should be written on them except for the figure/table number. When you
first refer to a figure or table in the main text, insert a box conveniently between two nearby paragraphs
which says, for example:
______________________________________________
INSERT FIGURE 3 ABOUT HERE
______________________________________________
However, in your lab reports, you may also choose to include the figures in the running text at the point
at which they are cited. In this case, put the figure or table number and caption below the corresponding
figure or table. Make the caption distinguishable from the running text (e.g., by using a smaller type size
and/or narrower margins).
Header/footer and formatting
Please include either a header or footer for your paper that includes your name and a page number. You
can set it up to skip the header/footer on the first page if you so choose. All papers should be doublespaced (except for the references section as mentioned above).