PHYS 334 Report Style Guide

Writing a technical report – such as the kind required for PHYS 334 – has many key differences from writing a history report or an essay. This style guide is meant to help students learn how to appropriately and clearly communicate scientific results to their peers and will highlight both broad structure and fine details in crafting experiment reports.

1 Writing the report


1.1 The "purpose" of a lab report

The lab report is a presentation of a student’s work, both in-lab and out. It is not a list of answers to questions or a fact-dump, and it is not just the collected data or analysis. Instead, a lab report is (or should be) a cohesive narrative that tells the reader a story – why the experiment matters, how it was done, what was found, and what the results and analysis mean. The student will be graded on the quality of the experimental work, but they will also be graded on the strength of the argument presented. 

Consider the data: a good lab report should detail both how and why the student collected the data, in addition to providing the numbers.

Consider the analysis: a good lab report should properly analyze the data, but it will also explain why the chosen methods are correct (e.g. motivating a particular model, or pursuing an iterative process where an initial analysis leads to new question, which lead to more data, which lead to new analysis…).

Consider the discussion: a good lab report should present a well-reasoned conclusion based on the analysis, and should describe the broader context of how this result fits into the larger sphere of physics (e.g. by comparing to other results or literature values, or by explaining how the technique, analysis, or approach could be improved).

Given the nature of experimental work, there is no such thing as a “right answer.” Instead, a student's goal for the lab report is to convince the reader that they understand both the big picture and the details, and that they have done the best they can with the data they collected.

As mentioned above, a lab report is somewhat different from a published journal article. For example, a lab report may provide more details regarding method or apparatus than an article would. Or, whereas a journal article author may simply present a plot with error bars or a final result with uncertainties, student lab report authors should also give a detailed account of how they estimated and propagated the uncertainties on those points. The student should expect their reader to know some general physics, but have no experience with the particular experiment discussed in the report.

1.2 Organizing the report

In general, a report should include the following material (though the author may combine sections under different headings or use different titles). This list is not complete; it is meant only as a starting place and students should carefully consider what is needed for each individual experiment.

Abstract

  • No more than one paragraph, the abstract should be a concise summary of the whole report including context/justification for experiment, main results, and conclusions.

Introduction, theory, and methods/procedure

  • Introduction
    • The author should provide context and justification for the experiment, and can mention other work or broader implications.
    • Theory
      • This section should briefly introduce the relevant phenomena to be tested and should provide equations (no derivations) that will be used later in the report.
    • Methods and procedure
      • include details on the apparatus and techniques used. This section does not need to be a “how-to”, but should give the reader an idea of how the measurements were carried out.
      • More details on specific procedures may be necessary for certain experiments. For example:
        • explaining the logic of the electronics used in coincidence measurements;
        • detailing how discrimination can be used to filter out unwanted data; or
        • specifics regarding calibration or characterization of the detector.

Results and analysis

  • Data and analysis can be presented separately or together, as seems appropriate for each experiment.
  • Provide data tables and/or plots, but avoid “fact-dumps”.
  • Figures are almost always better than lists of numbers.
  • If there is a lot of data, consider providing only representative data or plots in the main report, with the remaining placed in an appendix.
  • Provide fits where appropriate, motive the fit models, and include relevant fit information and best-fit parameters.
  • Provide representative examples of calculations when illustrative (especially for error propagation).
  • Discuss error estimates (both systematic and statistical) and detail uncertainty propagation.

Discussion and conclusion

  • Place your results in context. Compare with expectations and/or literature.
  • Discuss the quality of the analysis and reliability of your interpretations.
  • Include discussion of issues that arose or remain, and include some thoughts on improvement to the experiment if possible.
  • Summarize the take-away points for the reader.

1.3 Writing precisely

Science communication hinges on clear language. Avoid wishy-washy statements (i.e. statements that are ambiguous or which do not make a strong statement or argument), and be precise and quantitative whenever possible.

  • Use terms correctly and define them carefully for the reader when necessary.
    • Any new or unfamiliar physics terms should be spelled out on first use.
    • Always explicitly define variables used in equations. 

EXAMPLE: We never “measure” a photon; we measure some property of the photon (e.g its energy or frequency).

  • When discussing results, be quantitative and make direct comparisons (with error bars) whenever possible.
    • Talk about consistency and/or discuss probability based on standard deviations.
    • Avoid qualitative descriptions like “pretty close” or “good”.

BAD EXAMPLES:

  • “I feel like our results match expectations…” or “I like this value …”
  • “The results are pretty good.” or “The value is close to the literature value”
  • “Our value of 7 +/-2  A is not too far from the expected value of 15 A given how hard the experiment is.”
  • “We are happy with the results.”

GOOD EXAMPLES:

  • “Our value of 3.5 +/- 0.4 ns is consistent with the literature value of 3.848 ns”

1.4 Discussion

For more information, see all the page  Drawing Conclusions.

The discussion section is very important! It should not be an afterthought when writing the report. The discussion section is where you place your results in context.

  • Discuss agreement with literature or expectations.
  • Call out and discuss discrepancies. Give plausible and concrete suggestions for how these discrepancies can be explained or reconciled.
  • Discuss the quality of the data and fits and comment on the uncertainties.
  • Call out and discuss any points of concern.
  • Discuss any attempts you made to improve the data collection or analysis, even if they did not lead to better results.
  • Give further suggestions for improving the apparatus or measurement technique if possible.
  • When possible, give broader context (other experiments or other related theory or phenomena) to help explain and interpret the results.

Conclusions need to be quantitative whenever possible.

  • Use statistics – propagate errors (include details) and show error bars on plots.
  • Include (and discuss) goodness-of-fit parameters (e.g. reduced chi-squared) when appropriate.

Avoid speculation, and instead make statements that you can justify or support

  • If a result does not match expectations, do not just list every possible problem.
  • Come up with concrete ideas for what may explain the result and follow-up when possible.

BAD:

  • “Human error”
  • “Bad data”
  • “Could have taken more/better data”
  • “Could have done more/better analysis”

GOOD:

  • “We thought that placing the scatterer too close to the detector may have led to an increase in the count rate, since photons which normally would have scattered out, may have instead been scattered in. Retaking data with the scatterer further away led to count rates more consistent with our expectations.
  • If you cannot test a hypothesis, at least discuss what impact (magnitude, direction) it would have on the final result

GOOD:

  • “If the magnetic field reading were systematically low, that would lead to a final value for the magnetic moment that was higher than the real value, consistent with what we find.”
  • “We found a large uncertainty in the timing, because there is ambiguity in when the process actually begins and stops. Modifying the apparatus so that [blah, blah] would make the transition cleaner and would bring that uncertainty down.

1.5 Uncertainty analysis

As this is an introductory course in experimental methods, a big part of the aim is to teach good uncertainty analysis. For that reason, the graders will be especially keen to see how you estimated uncertainties, quantified statistical and systematic effects, and propagated uncertainties. You must discuss your error analysis in every report, whether it is explicitly stated in the rubric or not. 

A longer discussion of uncertainty analysis can be found on the page Uncertainty Analysis and Significant Digits.

2 Formatting


2.1 Plots

All plots included in the report should be done with python (or an equivalent high-level scripting language or software package); Excel is not a suitable program because the fitting and plotting commands are limited and do not allow users to produce professional-looking plots.

General points to keep in mind when making plots include the following:

  • Axes should be labeled with the quantity (and/or variable) being plotted and the unit.
  • If multiple sets of data are plotted on the same figure, a legend (or clear description in the caption) should make clear how to identify each set.
  • When plotting raw data, individual points should be shown rather than points connected by a line.
    • If error bars can be added without distracting from the readability, they should be explicitly shown.
    • If such error bars will obscure other data or make the plot look cluttered, a appropriate description of the uncertainties can be included in the caption instead.
  • When plotting fit functions, a continuous line may be used, but it should not extend beyond the range over which fit data was used. If you wish to extend a fit function beyond the data range, use a dashed line and indicate in the caption.
  • Titles are optional, but should be descriptive rather than a simple rehash of what appears on the axes. Avoid titles like “Magnetic field versus frequency” in favor of titles which provide new information like “Resonance points.
  • If including annotations on the plot (e.g. to report fit parameters or to indicate values or points of interest), make sure that the normal rules regarding significant figures, units, and overall formatting are followed. If the annotations are so numerous as to be distracting, consider removing them to the caption or to a separate table.
  • Avoid excess whitespace.
  • Make sure that all points and lines are visible. Do not obscure data with annotations or legends. Extend the plot range if necessary if the first and/or last data point is cut off. Consider using a logarithmic scale if significant portions of the data are crunched into a small area.

Example plots are shown in Figs. 1 and 2.

Figure 1: A good example of a simple data set and fit. Note the error bars, fit (and annotations), clear legend, properly labeled axes, and descriptive title.
Figure 2: A good example of spectrum plot. Note that this time, error bars have been omitted (they would clutter the figure) and that a sub-set of data (that used in the fit) is highlighted.

2.2 Figures and tables

Figures and tables should be numbered and each figure or table should have a caption which concisely describes what is shown. The caption and plot should be “stand-alone”, i.e. they should make sense when read in isolation without requiring reference to the surrounding text. (That is not to say the caption needs to be 100% complete… just that a person who flipped ahead or back in the report to a figure could reasonably understand what it shows.)

Figures and tables should be referenced in the text in the form Fig. n or Table n. When beginning the sentence with a reference to a figure, spell out the word “Figure” completely.

EXAMPLE: The fit to the data collected on Day 1 is shown in Fig. 3 and the fit parameters are listed separately in Table 1. Figure 4 shows the fit to the Day 2 data.

2.3 Significant figures

All numbers and uncertainty reported must include the appropriate number of significant figures. 

2.4 Equations and mathematics

Variables should be italicized, but numbers and mathematical symbols should not (non-italicized characters are often referred to as Roman). Descriptive subscript or superscript labels should not be italicized, unless the label includes a variable. Vectors should be bolded or marked with an overarrow. Unit vectors should be indicated by a “hat”.

Object Examples LaTeX
Variables, numbers, and symbols $a$ a
$B$ B
$\alpha$ \alpha
$3x^2 = 9\unicode[Times]{x3C0} = 9\pi$ 3x^2 = 9\unicode[Times]{x3C0} = 9\pi
Labels, subscripts, and superscripts $V_{\textrm{RMS}}$ V_\textrm{RMS}
$n^\textrm{(lit)}$ n^\textrm{(lit)}
$\beta_\mathrm{x} \neq \beta_\mathrm{y}$ \beta_\mathrm{$x$} \neq \beta_\mathrm{y}
Vectors $\mathbf{x}$ \mathbf{x}
$\vec{v}$ \vec{v}
$\overrightarrow{v}$ \overrightarrow{v}
$\hat{z}$ \hat{z}

Units should not be italicized and should be separated from the number by a space. They may be abbreviated or spelled out completely. Use appropriate SI abbreviations for units. For example, Hz, not hz for hertz, and keV, not Kev or KeV for kilo-electron volts.

Correct $x = \textrm{3.5 km}$ x = \textrm{3.5 km}
$\omega = 2\pi \textrm{ radians per second}$ \omega = 2\pi \textrm{ radians per second}
$\omega = 2\pi \textrm{ rad/s}$ \omega = 2\pi \textrm{ rad/s}
Incorrect $x = 3.5 km$ x = 3.5 km
$x = \textrm{3.5KM}$ x = \textrm{3.5KM}
$\omega = 2\pi \textrm{ rads per s}$ \omega = 2\pi \textrm{ rads per s}
$\omega = 2\pi \textrm{ rads per s}$ \omega = 2\pi \textrm{ rads per s}

Reported numbers should include uncertainties and units whenever appropriate. It is always preferable to indicate the number and uncertainty together, before giving the unit, rather than list the two values separately. The preferred format is $n$ +/- $\Delta n$ or $n \pm \Delta n$

Preferred $v = (51 \pm 3) \textrm{ m/s}$ v = (51 \pm 3) \textrm{ m/s}
Less Preferred $v = 51 \textrm{ m/s} \pm 3 \textrm{ m/s}$ v = 51 \textrm{ m/s} \pm 3 \textrm{ m/s}

In the case of scientific notation, this same philosophy applies to grouping the prefactors together before giving the common exponent.

Correct $v = (51.0 \pm 0.3) \times 10^{-3} \textrm{ m/s}$ v = (51.0 \pm 0.3) \times 10^{-3} \textrm{ m/s}
$v = 0.0510 \pm 0.0003 \textrm{ m/s}$ v = 0.0510 \pm 0.0003 \textrm{ m/s}
$v = 51.0 \pm 0.3 \textrm{ mm/s}$ v = 51.0 \pm 0.3 \textrm{ mm/s}
Incorrect $v = 51.0 \times 10^{-3} \pm 0.3 \times 10^{-3} \textrm{ m/s}$ v = 51.0 \times 10^{-3} \pm 0.3 \times 10^{-3} \textrm{ m/s}
$v = 51.0 \times 10^{-3} \pm 3 \times 10^{-4} \textrm{ m/s}$ v = 51.0 \times 10^{-3} \pm 3 \times 10^{-4} \textrm{ m/s}
$v = 0.0510 \textrm{ m/s} \pm 0.3 \textrm{ mm/s}$ v = 0.0510 \textrm{ m/s} \pm 0.3 \textrm{ mm/s}

Short equations and equations which will not be used later can be written inline. Longer equations and equations which will be referenced later should be placed on their own line and numbered. Equations (and single variables) should be treated just like any other word when placed within a sentence. This means that equations (and variables) should include proper punctuation before or after (if applicable) and can be placed anywhere within a sentence.

EXAMPLE: Recall that the total relativistic energy, $E$, of a particle of mass $m$ is $E = mc^2$ , where $c$ is the speed of light. On the other hand, the classical kinetic energy, $T$, of a non-relativistic particle is

$T = p^2/2m$, (1)

where $p$ is the particle's momentum.

When referencing an equation in the text, use the format Eq. (n). When beginning the sentence with a reference to an equation, spell out the word “Equation” completely.

EXAMPLE: We fit the data to Eq. (13) and extract the slope, $\gamma$ . Equation (14) relates $\gamma$ to the mass of the Higgs boson.

2.5 Citations and references

Include appropriate references (including to the lab manual or pages from the wiki) for both text and figures.

  • If using an idea or fact which is not your own, or if reproducing a figure, a citation is necessary. Place the citation in the text or caption at the proper location.
  • A general reference list at the end is not sufficient; you must additionally cite each use of a resource in the text.
  • When using direct text, reproduce the text exactly and use quotation marks or block quote formatting. Again, include a citation in the text at the appropriate location.
  • Include a reference list at the end of the report and format it appropriately.
  • We do not ask for any particular style, but be consistent throughout the report.

REVIEW THE UNIVERSITY PLAGIARISM GUIDELINES. We have ZERO TOLERANCE for students who plagiarize and cases WILL be referred to the Dean of Students.

3 Advanced topics


3.1 Appendices and attachments

Use appendices (in the same PDF document as the rest of the report) to include additional information (e.g. data or additional plots, tedious calculations, sidebar theory, etc.) without breaking the flow of the main report. 

  • If there is a single appendix, you may title it Appendix. If there are multiple appendices, you should number or letter them.
  • All appendices should include at least some text for context. Don’t just plop down figures or math or tables, but instead give the reader enough information so that they can make sense of what they are looking at without returning to the main text.
  • Reference all appendices at the appropriate place in the main text. An appendix should not just be a tack-on, but should be thought of more like “a really long footnote” for some topic in the report.

Avoid attachments and data dumps.

  • We DO NOT want to see your code.
  • We DO NOT want to see large amounts of raw data.
  • It is fine to include tables of data when it is relevant, but it is not appropriate to include, for example, the straight output of from a detector or an attached Excel spreadsheet of collected values or intermediate calculations.
  • Use your judgement to decide what is appropriate. Make plots and graphics when possible to handle large data sets.

Provide context.

  • We DO want to see context for all plots and calculations. Integrate this information into the main text or relegate to an appendix with appropriate accompanying text.
  • All plots and calculations should be discussed in words and referenced appropriately.
  • Good example: “We find that the temperature increases linearly with increasing voltage, and a fit of the data yields a slope of 5.04 +/- 0.08 K/V. (See Fig. 4.).
  • Bad example: “Plots and fits are shown below.”

Limit how much you direct the reader to the manual for more information. If the material is key, it should be included, even if you choose to quote directly.

  • On the other hand, remember that the report is not intended to be used to recreate the exact experiment, so there’s no need to give every detail; keep it focused.

3.2 Abstracts

Abstract are short, but very important. Look over our dedicated page,  Writing an Abstract, for more information.