How to write a lab report

A guide for undergraduate science, technology and engineering students

Personalise

Structure your lab report effectively to communicate your research

In the science, technology and engineering fields, laboratory reports are used to communicate research and investigations. As an undergraduate student, it is important to become competent in writing lab reports to prepare you to write the complex research reports that will be required in later study.��

Tips for scientific writing

Always write in full and grammatically correct sentences.
Be concise. Use one word instead of a phrase where possible and remember that long sentences can confuse readers.
Be objective. Limit your use of personal pronouns ("I", "you" and "we"), emotive language ("wonderful", "useless", "lovely") and casual or ambiguous expressions.
Use technical terms correctly. Learn what they mean, how to use them and how to spell them. Your lecturer may be able to recommend a good specialist dictionary.��
Avoid using contractions ("isn't", "doesn't", "it's"). Write "is not", "does not" and "it is" instead.��

Writing a lab report

Your lab report should provide a factual and accurate account of your investigation. It should cover:

What you did
What you found
What your results mean

Most schools will provide a structure for you to follow. There will be some variation in structure and expectations between schools. Some schools may have the introduction and methods already completed, and require you to carry out the experiment and record your results and interpretations. Others will require you to plan and write your report from the beginning.��

Lab reports can be presented in two key formats: the simple lab report and the extended lab report. Each serves a its own purpose in scientific writing.��

Writing a simple lab report

The simple lab report is generally two-to-five pages long and usually consists of the following:

Your aim is the purpose of your experiment.

You may have one aim or several. For instrumentation-based practicals, it is customary to mention the apparatus to be used. For example, the aim for a biochemistry practical that uses a spectrophotometer to determine serum protein levels might be written as "to determine protein levels in normal serum samples by spectrophotometry".

Mark as done
Your method is how you carried out your experiment (and what reagents you used).��

Depending on your school, the method is often given out as part of the practical notes. If this is the case, you would not typically need to rewrite it, although you may have to note any alterations.��

Some lecturers will be happy with a reference to the method. For example, "see practical notes page xx - alterations noted". Other lecturers may require a photocopy of the method attached to your report (with any alterations noted).��

Mark as done
Your results section covers what you found in your experiment.

This is where you record your raw data. Record data in tables and use the tabulated data to create graphs. Then, record any data you have determined from your graph in a separate table.��

For example, if you are trying to determine protein levels by spectrophotometry, you would record all the spectrophotometry readings for your standards and samples in the first table. You would then use these standard readings to construct a graph of protein concentration versus absorbance readings (a standard curve). The concentration of samples can then be worked out from the graph and presented in a new table.��

Tip: if the amount of raw data is excessive, consider presenting it as an appendix.��

Mark as done
Your conclusion should be an interpretation or summary (not a discussion) of your results.

This is normally a brief statement, for example "the concentration of protein in serum sample x was found to be x g/L, which is within the normal reference range". It may even be a tabulated summary of your results.��

Your conclusion should always reflect the question(s) posed in the aim(s).��

Alternative structures:

In some cases, your conclusion section will be combined with the discussion section of your report.

In other cases, your conclusion may be required to go after your discussion. In this instance, it would not be a summary of your results but what you conclude based on your discussion. This type of conclusion will probably be about a paragraph in length, recorded in a separate table. If the amount of raw data is excessive, consider presenting it in an appendix.��
Mark as done
Your discussion should cover what your results mean.

Were your results as expected? If not, why not? For example, a result outside the normal reference range could indicate one or more disease states, which should be mentioned.��

It is usual to run a positive and negative control with any analysis as a way of making sure the method worked. This should be in the form of a normal and abnormal control of known value for a practical like the serum protein analysis. If these controls give results within their expected ranges, you can generally assume your sample result is valid. If not, this is a good indication that something went wrong elsewhere.��

Sometimes the controls are past their expiry date, which means you have no way of knowing whether your results are valid. If your results are not as expected (as frequently happens in biochemistry practicals), do not panic - you can often score excellent marks by being able to explain what went wrong.��

Mark as done
Your references should be a list of sources you consulted for your discussion.��

How to reference

Mark as done

Writing an extended lab report

An extended lab report may be 10 pages or longer. It consists of the same components as a simple report, along with some additional sections.��

Additional sections in an extended lab report may include:

Including a table of contents is a good idea if your report is long or complex, especially if it has many different sections.��
Your introduction should be one or more paragraphs that define the subject of your report. For example, if the subject is High-Performance Liquid Chromatography (HPLC), you might define HPLC and outline how it differs from traditional liquid chromatography techniques.��
Write several paragraphs that describe the instruments you will use to perform your analysis and how they work. Examples might include a spectrophotometer or gas chromatograph.��

It is a good idea to include a block diagram of the basic components of the instrument. Use subheadings if you are using a complicated instrument capable of running several types of analyses.��
In reports that deal with instrumentation, the applied theory section is usually an explanation of the mathematics involved. Typically it will include several equations.��
The principles section of your lab report will include more equations. You will usually only need to include this section in your lab report if one or more chemical reactions are involved.��
If your method is to be presented as "Materials & Methods", this section is unlikely to be required. It is most often asked for when highly toxic reagents are being used.��
Preparing a flow chart will allow you to use your lab time as efficiently as possible.��

A flow chart is another way of describing your method. It is an easily read and logical sequence of events, allowing you to get long incubations underway as soon as possible. Sometimes you may not be allowed into a practical class unless you have a flow chart ready.��
Your calculations will usually be to work out what dilutions of stock reagents are required to prepare working solutions, in the case of biochemistry practicals.��
Sometimes your raw data will be excessive. It may be best to include your raw data at the end of your lab report as an appendix and put a summary of these results in the results section of your lab report.��
An extended lab report may, in addition to your discussion references, include references for your introduction, instrumentation and applied theory sections.��

How to reference

This guide was prepared by Deanna Jones and Pam Mort © ��¼�. For enquiries and suggestions, contact Academic Skills (academicskills@unsw.edu.au). This guide may be distributed or adapted for educational purposes. Full and proper acknowledgement is required.