Guide
to writing a formal report:
Your formal lab report should follow a
standard format with several clearly marked sections. The first page should contain the title, your
name and the names of your lab partners, and the date. The rest of the report should have the
following sections, in order: Abstract, Introduction, Experimental Procedure,
Results, and Discussions/Conclusions.
You should assume that your readers are at the same level in physics as
you, but that they have not read your lab handouts.
At the end of this hand-out is a checklist listing the
sections of a formal lab report, and showing various elements which need to
appear in each section. The point values assigned to each section will vary
from one report to another, depending on the specific emphasis for each lab,
but some version of this checklist will be used to grade each formal lab report
assigned, and will be handed back with the graded reports.
Taking the
most controversial element first, at least one-third of the grade for each lab
report will be based on the general quality of the writing. This includes
elements like grammar, spelling, and proofreading.
Calling this
“wildly unpopular” would be an understatement, and students almost always react
to this section by saying “Why do you grade on writing? We’re scientists and
engineers, not English majors.” This attitude is dead wrong: clear
communication is at least as highly valued in the sciences as in the
humanities.
As a
scientist, you can go into the lab and take data worthy of a Nobel Prize, but
if you can’t explain the results of your experiments clearly and concisely in
written form, you may as well not have done them. The key to all of modern
science is reproducibility— for a result to be accepted as the correct result,
other experimenters need to be able to reproduce the result. For that to be
possible, you need to be able to explain to other researchers all around the
world what your results were, how you got those results, and why those results
are important. If you can’t write clearly, you’ll never succeed in
communicating your results well enough to get the credit you deserve.
The key to
good writing is organization. A lab report, like a scientific paper, should
have a clear and logical flow of ideas: first explaining the motivation of the
experiment, then the procedure, then the results, then the conclusions drawn
from those results. The reader should be led smoothly from one idea to the
next, not tugged erratically back and forth between procedure, results,
motivation and conclusions.
On a finer level, each sentence and each paragraph should have
a clear point, and serve to advance the argument being presented. Writing is
more than simply stringing together a disjointed collection of unrelated
thoughts. “Stream of consciousness” lab reports are confusing and difficult to
read, and create the impression that you don’t actually know what you’re
talking about. Such an impression would be disastrous for a scientific paper,
and will accordingly be marked down in a lab report.
An even more basic element of good writing is proofreading.
There is no better way to make yourself look foolish than to turn in a written
document with a huge, glaring spelling error in the first paragraph (especially
in the current age of automatic spelling checkers in word-processing programs).
Before you hand a lab report in, read it over, or have your lab partner read it
over. Make sure the report makes sense, and that all the words are spelled
correctly and used correctly. The spelling check on Microsoft Word (or
any other word processor) won’t catch typos which end up matching real words
(“precious” for “previous” and “preformed” for “performed” are common errors of
this type).
Abstract: Summarize your experiment in one short
paragraph. State the purpose, the
experimental method, and the result. Be
concise--for example, often just giving the name of the method is
sufficient. If you have made a
quantitative measurement of some quantity, state the result of the measurement,
with uncertainty. Remember to include the appropriate units on any results that
you present. This
paragraph should “stand-alone” and not refer to figures or text in the
main body of the report.
Introduction: Discuss any relevant theory and/or motivation
for the experiment. This section serves
primarily to help the reader understand the significance of the experiment and
all the issues that are later addressed. The main questions to be addressed in
this section of the report are “Why are you doing this experiment?” and “What
do you hope to find?”
(Please note
that “We’re doing this experiment to illustrate the concepts discussed in
class,” while true, is not an adequate answer to the first question. When
writing the report, pretend that you have chosen to do the experiment of your
own free will, motivated by scientific curiosity, rather than having the
experiment forced upon you by the inhuman taskmasters of the Physics
Department.)
If the experiment is designed to test a particular physical
theory discussed in class, you should describe both the general theory and the
particular prediction you’re attempting to check in the Introduction. This section is often the most difficult to
write, and you may want to try writing this section last, since you want to be
sure to introduce any important concepts that are needed for your discussion in
later sections.
Experimental
Procedure: Describe your set-up
(drawings are usually needed) and the method used. Do not just restructure the instructions in
the lab hand-out, and do not assume that your reader has read the lab hand-out.
Make sure you describe the apparatus before referring to parts
of it. A Procedure section which starts out “We moved the cart back and forth
on the track and recorded the position with the sensor” will be
incomprehensible to a reader who was not in your class. You need to tell the
reader that the apparatus consisted of a cart, a track, and a sensor, and also
what kind of cart, track, and sensor you used. Including a sketch of the
apparatus is not sufficient description; you must also describe the apparatus
briefly in words.
Do not include unimportant details, such as where a particular
switch is, what combination of keystrokes and mouse-clicks you use to do
something in Science Workshop, or how you line up your head to see
that something is aligned. In
particular, you do not need to include steps like “Then we made a graph of
position vs. time and printed the graph out”-- attaching the printed graph of
position vs. time to the lab report is sufficient. It’s also not necessary to
identify the software packages used to generate graphs and tables, though it is
important to identify the software used to acquire data. For example, “We
recorded the position as a function of time using the Science Workshop package”
is important, while “We entered numbers into a data table in Microsoft Excel”
is not.
Explain what you did in the course of the experiment, but don't
write the procedure section like an instruction manual. Use the most direct
descriptions possible, writing in past tense and active voice. For example,
it’s better to write “We measured the length of the track using a meter stick”
than “The length of the track was measured with a meter stick” or “Use a meter
stick to measure the length of the track.”
Include measurements that are related to the limitations of
the experiment, such as a measure of the amount of error in a particular
measurement. You will discuss these
errors in more detail in the Results section, but how you measure them and what
you measure them to be is relevant to the procedure and so needs to be
discussed in this section. They belong
in this section because they give a quantitative measure of the accuracy and
reliability of the results.
Results: Present your data and calculations. This is the meat of your report.
First present
the raw data. Numerical data should be
listed in a table and the table referred to in the text; graphical data (for
example, y vs. x plots from Excel) should be presented as figures and referred
to in the text. Be sure to include
uncertainties in any measured quantities.
After presenting the raw data, discuss any calculations that you
made from that data. If there are
results of calculations that would be best presented in a table, make sure they
are clearly distinguishable from the raw data, either by putting the processed
data in a separate table, or by clearly labeling the columns. If there are
results that would be best presented in a figure, label the figure clearly, and
be sure to refer to it in the text. Be
sure to label the tables and figures and to refer to them in the text by name (e.g.
“Figure 1”, “Table 2”). Don't include a
figure without discussing it in the text.
Explain the relevance of the figure, and what it tells you about the
experiment.
Be sure to include an uncertainty with every measurement (see
the separate document on uncertainties).
In general the discussion of the measurement
of the uncertainty (that is, how you determine the value of the uncertainty) is
given in the experimental procedure section, but you still need to give the
uncertainty (after a plus-minus sign) when presenting the results. Say “We measured
the mass of the cart to be 1.02 ± 0.03 kg,” not “The mass of the cart was
1.02.”
Discuss your errors in this section. Discuss the sources of error, both random and
systematic, and how the errors affect your results. Do not put off the discussion of the error
until the Conclusion section.
Discussion/Conclusions: If there are further interpretations of the
results or significant implications to be discussed, such a discussion should
occur in this section. You must also
summarize the main results of the experiment.
This is where you should discuss the implications of the
comparison between experiment and theory (Does your measurement agree with the
theoretical prediction? If so, what does that tell you? If not, why not?) , or
between two different methods of measurement (If you measured the same quantity
in two different ways, which measurement was more accurate?). Address any additional ideas you have about
the experiment, such as improvements that could be made, or how the experiment
relates to the material discussed in class. Use this section to be creative,
wax philosophic, scale lofty heights of rhetoric.
Additional
guidelines: There are some more
general mistakes in writing reports that appear to be fairly common:
Error
and Uncertainty: The most significant common mistake is stating "the
percent error" as the "uncertainty" in your result. Many students calculate the percentage
difference between their result with the
"correct" result. This is NOT
the way to calculate uncertainty.
You should imagine that the lab experiment is an actual
scientific problem to be investigated. The whole reason for doing the
experiment is that you don't know the correct answer and want to determine it.
The uncertainty is a measurement of how well you’ve done your measurement, and
how much confidence another researcher should have in the result, not a
measure of how close you’ve come to a hypothetical “correct” answer. By quoting
a “percent error” from some “correct” value, you’re
saying both that your measurement is wrong, and that the experiment was
pointless in the first place: if you knew the correct answer, you wouldn’t need
to do the experiment at all.
You can (and often
should), however, discuss "the percent disagreement" or “percent
difference” between your result and the theoretical prediction. Such measurements are an important part of
determining the usefulness of a particular theory, but are not related to the
uncertainty associated with a given measurement. This may seem like a trivial
semantic distinction, but it’s not.
Figures
and Tables: Another very common (and annoying) mistake made by students
is neglecting to label the figures and tables and/or to not refer to them in
the text. Figures and tables are crucial
components of a science paper should be able to stand by themselves. They should include a short caption or
descriptive label, telling the reader at a glance what is being presented. If
multiple quantities are plotted in a single figure, the different data sets
should be clearly distinguished (using different symbols or line styles, with a
key to the symbols or styles included in the caption or the figure
itself). Figures and tables should also
be referred to at the appropriate points in the text, to be sure to draw the
reader’s attention to the data.
Figures and tables should be assigned numbers according to the
order in which they appear in the text, and should be referred to by number (e.g., “A graph of velocity vs. time is
shown in Figure 1” or “The data for the second trial are shown in Table 2.”).
Tables and figures are numbered separately—the first figure is “Figure 1,” and
the first table is “Table 1” regardless of where they appear in the text..
Equations: Equations that appear in the
text should be put on their own line, and centered in the text. When multiple
equations are used in a report, you should number them according to the order
in which they appear, and refer to them by number (e.g.,“As
we see from Equation 1, the force is proportional to the acceleration”).
When you
introduce a new equation, you should be sure to define all the symbols in it.
For example, if I want to refer to
Fnet = m a (1)
where Fnet is the net force
acting on an object, m is the mass of the object, and a is the acceleration of
the object.”
Marketing:
One last piece of advice: write the
report honestly--don't try to over-sell your results. If the results are only marginally
significant, you are better off stating clearly in the report that you believe
this to be the case. Others may still
find it interesting enough to follow up on your experiment. Over-selling of marginally significant
experiments suggests that the author of the lab report doesn’t actually
understand the material that he or she is talking about.
Academic Honesty:
You will work
on the lab experiments in groups, and you are always free to discuss your
results and the interpretations of those results with your lab partners.
Indeed, you are encouraged to discuss your results, and even discuss how best
to present the results.
What you hand
in your lab report, however, must be your own work, and only your own work. You
are not allowed to copy sections of a report from another person, or to write
sections of a report with or for another person. You can proofread your
partners’ reports, and ask your partners to proofread your report, but any
changes made to the text must be made by the person who will hand the report in
for grading (i.e., you can neither offer nor accept verbatim re-writes
of paragraphs in your report).
Lab
reports that are wholly or partly identical will receive a grade of zero, and
be referred to the Deans as plagiarized. If you have any questions
regarding the limits of acceptable collaboration on lab reports, ask your lab
instructor. Do not assume that the standards used in another class will apply
here, and do not attempt to guess what is acceptable and what is not.
Physics 111 NAME:___________________
Lab Report Checklist
GRADE:__________________
I) Abstract: 10pts
____ Summarize in paragraph form
____ State results
____ Uncertainty and units
II) Introduction: 20
pts
____ Discuss motivation of experiment
____ Describe theory being tested
____ Describe specific prediction of interest
III) Experimental Procedure 20
pts
____ Write out in paragraph form
____ Describe apparatus used
____ Include only important details
____ Explain measurements made
____ Include uncertainty estimates
IV) Results 30
pts
____ Write out in paragraph form
____ Clearly labeled
data tables
____ Units, uncertainties
____ Figures (where appropriate)
____ Labels on figures
____ Refer to figures and tables in text
____ Calculations from data
____ Errors and uncertainties in calculations
V) Discussion/ Conclusions 20
pts
____ Summarize results of experiment
____ Further interpretations. implications
____ Agreement/ disagreement with predictions
____ Comparison of methods (where appropriate)
____ Possible
improvements
VI) General Writing 50
pts
____
Organization
____
Sentence structure, grammar
____ Spelling, proofreading
VII) Other: