9. LABORATORY RECORDS AND REPORTS
by Dr. Donald E. Simanek
Lock Haven University
9.1 PREPARATION FOR THE LABORATORY
- Read the instructions before coming to lab. If you
have not received instructions at least one week before the
lab period, ask your instructor to supply them.
- Read the relevant background material in your textbook, or in
- Come to laboratory with a plan in mind, and at least
a preliminary derivation of the error propagation equations.
9.2 THE LABORATORY RECORD
Scientists and engineers record laboratory data in bound
notebooks with pre-numbered pages. These books serve as a
permanent record of the work, and can serve as legal evidence
in priority disputes. Some instructors insist that students in science
laboratories keep such notebooks. Whether required or not, the use of a
notebook helps you to develop good laboratory habits that
will serve you well in your future career.
Your laboratory notebook reflects your personal style, but you
should write it so that a co-worker familiar with the subject
of your research could understand it. Such a person may need
to obtain information from your notebook. You may need to
refer to the notebook at a later date, therefore do not omit
any information necessary to understand what you did, or to
Use a bound (not a loose leaf) notebook for the laboratory record. Make
notebook entries as the experiment progresses, as a running record of the
work. The notebook includes a complete history of all experiments
performed, and their results.
Quadrille-ruled pages with 1/4 inch squares facilitate making
data tables and rough graphs. Don't erase anything in a
laboratory notebook, and never remove pages from it. Line out,
and annotate, mistakes. Use permanent ink, for better
readability. You may abbreviate, but make all entries clear,
organized and complete"and neat enough for you, or someone
else, to read.
Here's a check list of items which you should record in the
- The date and time of each new record.
- The initials of the person making the record.
- Descriptive headings, titles, and subtitles.
- Lists of the equipment used (name, manufacturer, model
and serial numbers), with relevant specifications.
- Sketches of the experimental layout, circuit diagrams,
etc., with all components labeled.
- Observed data. Record data in the notebook
immediately; do not recopy it from scraps of paper. Organize
the data in neat tabular form, with ample space for
corrections and auxiliary notes. Symbols and notation of each
column heading should match that used in the equipment
diagram, equations, and other references in the discussion.
When possible, identify the exact instrument used. Neatly
line-out incorrect data. A large amount of incorrect data may
require you to line-out (or overlay with a large X) an entire
table. If you feel that an 'X' across a whole page looks
unsightly, use a footnote to label it as "deleted." Always
record the reason for such altered entries.
- Calculated results, prominently displayed.
- Sample calculations. Don't include every calculation,
but do include a sample of each type. If you need to do this
same sort of calculation later, the sample may save you time.
- Curves. Plot tabular data as curves whenever possible.
We use the term "curve" to represent data points plotted
with a smooth line drawn through them. The term "curve"
applies even to straight lines.
The term "plot" refers to roughly sketched curves,
perhaps done on the quadrille paper of the lab notebook.
The term "graph" refers to the more neatly produced and
annotated curves done on genuine graph paper, or in a
form suitable for publication.
Important data may deserve a graph made on genuine graph
paper, permanently attached to the notebook page. Avoid
using tape, for it deteriorates with age. Use a thin line
of glue to "tip in" such added material. Attach charts,
diagrams and photographs in the same manner.
- Graphs: All graphs (and plots) must have a descriptive title,
each axis labeled with quantity, symbol, and units.
Choose a scale size such that one may read values from the curves
with at least the same accuracy as the accuracy of the data.
Make the data points very small (some use pinpricks) and emphasize
them with small, neat circles. When you show several curves
on the same graph, group related data points in some way using
distinctive symbols, such as circles, triangles, and squares
(use a symbol template, for uniformity). Provide a key, on the
graph page, to the meanings of the symbols.
- Notes or explanations essential to proper performance
of the experiment or interpretation of the results. This might
include your explanation of how you overcame any difficulties
encountered in the experiment.
- A restatement of the questions posed, and your answers.
The reader won't expect the lab notebook to contain a condensed and
polished report of the experiment, but will expect to
find enough evidence to determine what you did, how you did
it, and what results you obtained.
9.3 THE LABORATORY REPORT
|Disorganized reports annoy and confuse the
© 2001 by John C. Holden.
The laboratory notebook provides a personal record documenting
the progress of the experiment. The laboratory report serves
a quite different purpose. It communicates your experimental
work to other persons. This demands a different style and
All "real" scientific work of any value (and some that isn't)
eventually finds expression in a written report. In industrial
research and development, reports communicate to supervisors
and directors, may circulate internally within the company,
and may even reach other scientists in the same field around
the world. Some reports get published in technical and
scientific journals. Even technicians sometimes write reports.
Many a scientist or engineer discovers the hard way that
people judge the quality of experimental work by the quality
of the reports. Ineffective reports may cause people to ignore
the research itself, and, on a very practical level, may
jeopardize the funding of that research.
Style and appearance of reports:
Essential parts of the report:
- Use good quality standard size 8 1/2 by 11 inch paper:
plain, unlined, and with no holes or ragged edges. (Some
instructors may accept handwritten reports on lined paper, a
practice considered unprofessional in a real work situation.)
- Leave at least a 3/4 inch margin on the top, bottom
and sides of the sheets.
- Organize the report for easy reading. The structure
and organization of the report should impress itself on the
reader even with a casual skim. Use headings and subheadings
to make the structure clear.
Here's a list of the usual parts of a complete report.
The nature of the experiment will determine the
necessary ones, and the appropriate heading for each.
- ABSTRACT. A brief (one paragraph) summary of the
purpose, method, and significant results of the experiment.
- PURPOSE (OR OBJECTIVES) OF THE EXPERIMENT (Don't
include this if your report has an abstract.)
- EQUIPMENT LIST, including any identifying model and serial
- BACKGROUND. A review/summary to acquaint the reader with facts,
theory, or research specifically relating to what you did in this
experiment.) Material readily available in any textbook needn't be
- MATERIALS, METHODS AND PROCEDURES. This tells the reader what
experimental methods were used. Apparatus or procedures unique to this
experiment must be described and explained. Standard procedures needn't be
elaborated, by should be referenced.
- RESULTS, including graphs, and tables of results, as appropriate.
- DISCUSSION OF RESULTS, and of their uncertainties.
- CONCLUSIONS (You may prefer to include this in the discussion of
Avoid unnecessary duplication. Don't include data and procedure in the
results section. Don't include minor details of procedure, theory and
results in the abstract. Include only material directly related to what
you did in the experiment. Omit idle speculation.
9.4 FORMAL AND INFORMAL REPORTS
The informal report differs from the formal report in three
major respects. The informal report omits: (1) the abstract,
(2) description of procedure (except where there were
significant deviations from the procedures of the instruction
manual), and (3) exposition of the physics underlying the
Your instructor may want a copy of your laboratory record
included as an appendix to the report, for completeness. This
will include the equipment list, original data, calculations,
preliminary graphs and sketches, record of observations made
in the laboratory, etc. The instructor may, in the informal
report, allow you to insert this after the "purpose" section
of the report, to preserve chronological continuity. Don't
expect that anyone will necessarily read this! Whatever you
want the reader, or instructor, to consider in evaluating your
work must appear in its appropriate place elsewhere in the
9.5 GENERAL CONSIDERATIONS OF REPORT WRITING
A real experiment may occupy months or years. The laboratory
record may consist of several filled notebooks, computer
printouts, photographs, charts, etc. You must distill,
reorganize and repackage this scattered source material into
a clear and concise document of a just a few pages. The report
must communicate efficiently. It must have a clear and logical
structure which allows the reader to extract the essential
Readers of your report want to know what you accomplished, and
you must say that clearly and effectively. Every experiment
has certain objectives, and you must state the extent to which
these were accomplished. If you set out to determine the
constancy of the acceleration due to gravity, you must, in
your discussion of results, state whether your experiment
demonstrated its constancy, and within what uncertainty. If
you set out to measure the size of the acceleration due to
gravity, you must give your one best determination of that
acceleration, along with its estimated uncertainty. These
statements must appear in the "results" section, even if they
appear elsewhere in the report.
- Condense and prune the presentation to make your
points effectively. Emphasize the important points. Don't
waste the reader's time with trivia.
- A good rule for improving your prose is:
WHEN IN DOUBT, LEAVE IT
- Don't clutter the text with calculations unless you
must explain something about them.
- Don't pad the text. Readers don't appreciate having
to read through trivial and irrelevant passages to find the
- Use genuine graph paper, not cheap substitutes. Every
graph must have a title, written out in words. Not: "T vs. L."
Not: "Period vs. Length." Rather, something more specifically
descriptive, like: "Pendulum period as a function of
suspension length." Choose the size of the axis scales so that
the graph nearly fills the page.
- Label each graph axis with the quantity, symbol, and
units plotted on that axis. Example: PERIOD (T) in seconds.
- Label the axis scales neatly and clearly. You must re-label
logarithmic scales on commercial log paper.
- Use tables for large amounts of data, especially when
you wish to display the relations inherent in the data.
- Column headings of tables must indicate quantity,
symbol, and units, just as graph axes do. Each table must have
a title and an identifying number, for reference.
- Indicate the errors (uncertainties) for all quantities.
Minimize the clutter within tables by grouping
information when possible. If all data entries in a column of
a table have the same absolute or relative error, put that
information at the top of the column only. The same applies
to unit labels, which you may place at the top of the column.
9.8 DISCUSSION AND ANALYSIS
- Show how you arrived at your uncertainty estimates.
- Show the error propagation equation(s) you used. Error
propagation equations motivate decisions about experiment
design and procedure. They also justify the uncertainties you
assign to results. If some error sources dominate others, this
fact may deserve comment. Tell how you designed the procedure
and strategy to minimize uncertainties. [You need not mention
the usual precautions; only those specific to the particular
experiment, or in some way unusual.]
- Make meaningful comparisons where appropriate. When
the experiment has numeric results that you can compare with
other independent sources, comment on that comparison. Do not
call this comparison the "error", call it the "experimental
discrepancy." When you can quote both error and discrepancy,
do so, and comment on their relative size. (A discrepancy
larger than the error certainly requires some comment!)
- The methods of science never prove anything. The word
"proof" refers to a strictly mathematical process. Nor does
science claim absolute truths. Avoid the word "truth" in
scientific discussion. In a single experiment you might
"verify" or "confirm" the validity of a physical law, in a
9.9 DISCUSSION OF RESULTS, AND CONCLUSIONS
YOU CAN'T EXPLAIN SOMETHING TO SOMEONE
IF YOU DON'T UNDERSTAND IT
- Your conclusions must relate to your stated purposes
or "objectives". Tell the reader to what extent your
objectives were realized.
- Don't claim more than the facts warrant. Support your
assertions with evidence, logic, or specific references to the
literature. State specifically what you achieved, and the
estimated uncertainty of the results, but don't make broad and
Students benefit from study groups, learning from each other.
Strongly resist the temptation to rely too heavily on others.
When exam time comes, you must work alone.
Laboratory partners discuss each experiment and share ideas.
But in a classroom situation the written report represents
your own work, not that of a committee. Don't let others do
your thinking and analysis.
Partners' data will, of course, consist of the same sets of
numbers, but each partner will organize the report to suit his
or her own personal tastes and style. Each will do the data
analysis independently. Partner's reports will, therefore, not
look alike, even superficially. When partners make identical
mistakes, this raises suspicions that one must have copied without
something wrong or absurd makes one appear not merely
unprofessional, but also thoughtlessly lazy! Signing your name
to a totally wrong statement copied word-for-word from someone
else demonstrates your inability or unwillingness to think the
matter through on your own. Better to make your own mistakes,
honestly. Better yet, use critical thinking to
discover your mistakes, and those of others.
When you write the discussion of results yourself you'll gain
the valuable experience of drawing your own conclusions,
unprejudiced by the opinions of anyone else. All details of
the report will reflect your individual style and individuality.
9.11 THINGS YOU SHOULDN'T DO
Don't include idle speculation about sources of error. To say
that certain conditions of the experiment "may have caused
error" communicates no useful information unless you cite some
specific evidence or a plausible mechanism pointing to that
Don't include such trivial comments as: "The resuslts may have
"human error." We all know that human blunders, misperceptions, and
misinterpretations can occur. We expect the
experimenter to take every precaution to avoid them. This
"goes without saying." The other classes of "human error" due
to limitations of instruments, and limits of human observation
of instruments belong in the quantitative error discussion.
Likewise, don't say "Error in results could arise from calculation errors."
If you mean blunders, this statement tells us nothing we
didn't already know (we still wouldn't know whether there were
blunders). If you mean the error introduced by calculating
devices, then you haven't done your job properly. Your
responsibility includes choosing calculation techniques that
do not introduce significant error. You should do everything
necessary to keep calculation errors negligible compared to
the experimental errors. If for any reason you did not, or
could not, accomplish this, you must give good reason why you
Most elements of good style common to other types of writing
also apply to scientific writing. One of the best general
references for the student is:
Strunk, William, Jr., and White, E. B. The Elements of
Style. Macmillan Paperbacks, 1962.
This book demonstrates by example the clarity and brevity
that it advocates.
The 1918 edition
may be found online and has very handy internal links.
Other useful references are:
- Menzel, Jones, and Boyd. Writing a Technical Paper.
- Vallins. Good Writing, Better Writing.
- Gunning. The Technique of Clear Writing.
- Flesch. The Art of Plain Talk.
On matters of technical style for research journals, consult
The American Institute of Physics Style Manual
. Consult the AIP website
for the most recent guidelines.
And still more about writing for the internet. 32 Resources for Better Online Writing by Brenda Barron.
Examples of style faults.
We list below some faults frequently found on student
laboratory reports, with suggestions for improvement.
(1) A report organized as follows:
Aside from the overuse of "we" this "chronological" style
doesn't convey any sense of the relative importance and
logical connections inherent in the material.
(2) "The acceleration of gravity, one of the most fundamental
constants in physics..."
This lacks content. It says nothing important. Stick to
the facts and avoid empty generalities and attempts at
"profundity." Also, gravity doesn't accelerate. This should
read "acceleration due to gravity."
(3) "In this experiment we proved the truth of the
law F = ma and measured the value of the acceleration."
This uses the words "prove" and "truth" in a questionable
manner. Reserve "prove" for mathematical theorems. Avoid
the word "truth" entirely in scientific writing. An
experiment may disprove a law, but no finite number of
experiments ever establish a law as absolutely true. The statement
also leaves ambiguity: "acceleration of what?"
(4) "We located the apparatus in the northeast corner of room 216 of
the science building, in a sunny spot on a maple table 31 inches
from the floor."
Extraneous details annoy the reader. Include only those
details you've shown to have some effect on the
experiment. Some other details may deserve a place in the
laboratory notebook, for future study may show that they
weren't insignificant after all.
(5) "I enjoyed this experiment very much and learned a lot
Save personal comments for other occasions. Don't include
them in the laboratory report. The reader may easily
misinterpret the motives behind such statements.
(6) "Due to poor equipment we didn't get good results."
No scientist ever has perfect equipment. The experimenter
must learn the limitations of the equipment and how these
affect the quality of the results. Sometimes experiments
using very crude equipment have confirmed or rejected a
law or theory.
(7) "Our results agreed exactly with the textbook value, so we
consider the experiment a success."
Even with the worst equipment and technique one may sometimes
accidentally obtain a zero discrepancy. This tells
nothing about the quality of the experiment. The limits
of uncertainty tell us the quality of the experiment.
(8) "A force of 9 kg stretched the spring 5 cm,
therefore it did work (9)(0.05)(9.8)/2 = 22.05 Nt. From this
we calculated the efficiency of the spring by..."
Don't clutter the report with routine calculations. We
don't fault the "force of 9 kg" in the first line. The
context makes clear that the writer means "A force equal
to the weight of 9 kg at the earth's surface."
(9) "The ladder contacted the wall at an angle of 60° so the force was perpendicular."
60° measured with respect to what? Which force, of several in the problem, what exerted the force and what did it act up on? Perpendicular to what? Beware of "it", "that", "these" and "those", for their reference object may be ambiguous.
9.13 LABORATORY ETIQUETTE
You and your partner will have an assigned work area or work
station, which no one else shall disturb. Your responsibility
includes keeping it in proper order. You will use equipment
and parts stored in trays or drawers in an orderly fashion.
Keep it in that order, for your own convenience, and out of
consideration for other students who will follow you.
Keep your work area uncluttered. Store all instruments and
components not actively in use in their proper place, away
from your work area, or in the special storage cabinets.
You may need other equipment and components stored in a
different area from your work station, perhaps in drawers or
bins, or on shelves in the stockroom. Return these to their
proper place immediately when you have finished with them.
Don't make unauthorized modifications to the equipment.
Don't use any kind of tape, markers, or ink on laboratory
Report damaged equipment or components to the laboratory
instructor, for prompt repair or replacement.
[An E-prime document.]
Document © 1996, 2010 By Dr. Donald E. Simanek,
Lock Haven University of Pennsylvania. It may not be sold or
used commercially for profit without permission of the author.
Teachers may freely use this document and distribute
it to students without charge provided it includes this copyright notice.
The author welcomes suggestions for additions and improvement. Send to:
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