Difference between revisions of "20.309:Lab Report Guidelines"

Lab report guidelines

The purpose of your report is to convey as clearly as possible which physical phenomena you examined in the lab, the means you employed, and what you learned. The report should be brief. Consider each pixel you choose to darken on the page in the context of the information it conveys. Ideally (but not practically), erasing a single pixel would diminish the report. Focus on the essentials. This does not mean you should use a small font.

Imagine you are writing the report for a classmate. The intended audience has a deep understanding of the subject. (Perhaps you need to imagine a different classmate.) As such, lengthy derivations and explanations are not necessary. The reader would very much like to understand what you did in the lab, what sort of problems you ran into, how you analyzed your data, and what you concluded.

Your report does not have to be written like a formal scientific paper. Feel free to use whatever organization works for you so long as it includes all of the information.

• Bullet points are often more effective than flowing text.

Brevity is not an excuse for imprecise, incomplete, or unclear communication.

Follow the content and style guidelines below.

Explain the apparatus and procedure

Some lab exercises involve significant design and construction work. Others utilize complex systems that were built by others. In either case, the apparatus you used in the lab must be documented in your report. Block diagrams, schematics, photographs, text descriptions, and citations of sources are all excellent ways to describe an apparatus.

Design documentation should be sufficiently detailed to enable another person to build a functionally similar piece of equipment. Include component values and reference designators (R_l, C_f, L₁, etc…) on schematics. Explain why you chose the values you did. If you chose to implement a portion of your apparatus differently than the lab manual suggested, explain why. If you wrote a program, explain what it did in the body of your report and include the source code in an appendix.

Detailed documentation is available for the predesigned pieces of equipment in the lab (such as the AFM and the optical trap). In these cases, focus on the aspects of the machine that are essential to understanding your data analysis. A simple block diagram and a few bullet points will meet the requirements.

Once you have documented the apparatus, explain how you used it and what measurements you took.

Explain your analysis

Your report must explain how you analyzed your data. It is unecessary to reproduce each step of every calculation; however, the account you give must make the process clear. If you wrote (or used) computer code, explain how the code works with bullet points and include the source code in an appendix.

Report results properly

All numerical results should be reported with an appropriate number of significant figures and an associated uncertainty or significance level. There should be no ambiguity about the units of all numbers reported. Use plots or tables to report multiple results efficiently.

If you are unsure how to compute the uncertainty of a numerical result, please ask an instructor.

Put results in context

Compare your results with expected values, possibly from literature or other lab groups. Indicate possible sources of error, whether the resulting error would be systematic or random, and how the effect of the error source could be mitigated.

Say what would you do differently next time

The instruments and procedures you will use in the lab are not perfect. Explain what factors limited your measurements how you could improve the results.

Answer questions posed in the lab manual

Ensure that your report addresses all the questions posed in the lab manual and by instructors. If there is not a natural place to do this in the body your report, put the answers in a section of their own.

Present data properly

• Figures must be numbered, descriptively captioned, and discussed in the text.
• Plots must have a brief, informative title. Axes must be labeled with a description, including units.
• Pictures must have a scale. (Pictures of your apparatus are an exception.)
• Chartjunk is forbidden.
• Use tables appropriately.
• Try not to use screen captures.

Do not present every piece of raw data you gathered. Put in only things that are important, in a clear and concise format. If for some reason you have a large body of extremely interesting data to present, put it in an appendix and refer to it in your report. If you have a large body of uninteresting data, leave it out.

Write tight prose

• Use bullet points.
• Avoid the first person.
• Use active verbs.
• Eliminate unnecessary words.

It is common practice in scientific writing to avoid using the pronouns I and we. This is changing slowly; however, it is an excellent habit to minimize the first person in your scientific writing. The author of a first person sentence in a scientific paper has frequently misidentified the true subject of a sentence. Consider the following 4 versions of a sentence:

1. I ran the experiment three times and calculated an average power of 1.21 GW.
2. The experiment was run three times and an average power of 1.21 GW was calculated.
3. Three experimental runs yielded a calculated average power of 1.21 GW.
4. Three experimental runs yielded an average power of 1.21 GW.

In this example, substituting the subject “The experiment” for “I” eliminated the first person pronoun in sentence number 1, resulting in somewhat preferable sentence 2. The second sentence, though, is undesirable because it contains the passive verb forms "was run" and "was calculated." Passive voice is common in scientific writing; however, that does not mean you are required repeat the offense.

It is impossible to completely eliminate passive sentences from scientific writing. But that doesn’t mean you can’t try. See if you can limit your use of the passive voice to fewer than tweny percent of the verbs in your report.

Sentence 3 is preferable to number 2 because it uses an active verb. But it still could be tighter. Average values are necesarily calculated. Unless required to differentiate between several possible averages, remove the redundant verbiage.

Write your own report

In 20.309, you will work collaboratively in the lab. The report you submit must be entirely your own work. Any words, data, images, code, or other intellectual property you take from somebody else must be appropriately cited. Plagiarism is unacceptable.

Lab report grading

Lab reports will be graded on a 25 point scale. An outstanding report:

• Demonstrates mastery of the theory and practical implementation of the key techniques used in the experiment.
• Presents results for each of the required experimental procedures
• Draws appropriate conclusions from the data
• Contains a thorough, correct, and well explained analysis
• Address shortcomings of the experimental procedure and problems that cropped up during experimentation
• Acknowledges everything that is not original work with an appropriate citation
• Is well communicated

Outstanding reports will receive a numerical grade of 23-25 points.

Reports with minor deficits in one or two areas will receive an excellent score in the range of 20-22 points.

Reports with important shortcomings in one area will be awarded 17-19 points.

Manuscripts not meeting the above criteria will be graded accordingly.