A Format for Lab Reports

A very important aspect of laboratory work is being able to communicate your results effectively. Although each teacher may have different preferences, there are certain, accepted standards for the preparation of a lab report.

The lab report is divided into several sections in order to organize the contents and make it easy for the reader to follow and to find the information he is looking for.

Title

            The title should be one simple sentence that describes the purpose of the lab. For example, if you are investigating how quickly a plant will grow in response to sunlight in a sunny window, your title might be “The effect of sunlight on plant growth.” Your reader should be able to tell what the investigation was about just by reading the title.

Introduction

            This section provides the reader with any background information or concepts s/he might need in order to understand what you have done in the investigation and it’s purpose. The Introduction defines the subject of the report. It should also mention the motivation behind the investigation. It is a good idea to write the Introduction last. This way, you can read through your report and try to imagine the kinds of questions a reader might ask. In our plant investigation, the reader might wonder why you used a sunny window and a dark cupboard, or why you harvested the leaves to check for starch. Your Introduction might explain what photosynthesis is and why it is dependant on sunlight as well as the role of the leaves. Try to avoid simply listing things. You would never write something like “Alcohol was used because . . . , a beaker was used because . . . , iodine was used because . . .” Make it more like paragraph form. Also, remember that you are trying to give some basic background, not a PhD in plant biochemistry. Assume that the reader has some knowledge in the area but is not an expert. Do not include information that is not relevant to the investigation. For the plant experiment you would not describe the soil the plant was grown in or the size of the cupboard. Conclude the Introduction with a brief statement as to the purpose of the investigation. After reading this section a person should have a good idea of what was done by you and why.

Materials and Methods

            You would be more familiar with calling this section a “Procedure” but many scientific journals refer to it as “Materials and Methods.” The Materials and Methods section contains the methods and equipment used to obtain the results; it tells the reader what you did. This section should contain enough detail to allow another scientist to repeat your investigation, but should not be overwhelming. It should not be a regurgitation of the lab manual. Any procedural changes from the original outline (lab manual) must be included, however. Do not use lists of equipment or a numbered list of steps that you followed. Rather, present the materials and methods as if it were a story. Mention the equipment or apparatus used as you describe the steps you followed in completing the investigation. Procedures are presented in chronological order for each part (avoid mixing investigational procedures even if this was what was done in the lab) and subdivided using paragraphs. Include items such as growth conditions, organisms, and the chemicals used in the investigation. Avoid using trade names or common names for chemicals (e.g., use sucrose not sugar); describe organisms with their scientific names (e.g., Vicia faba not bean). Examples of methods include sampling techniques, types of microscopy, and statistical analyses. Sources for major/unusual items (e.g., cell cultures, special chemicals, etc.) should be included. For specialized equipment (e.g., microscopes, centrifuges, etc.) the manufacturer and model should be included. Investigations described in a scientific paper must be reproducible. For this reason, the quality of the Materials and Methods section is judged by the reader's ability to repeat the investigation (and obtain similar data). If a colleague cannot repeat your investigation using only this section it is probably poorly written. This section is always written in past passive tense, as are all sections. This means that there are no references to the first person, or pronouns. For example, you would not say something like I/we/Jack/Jill looked added 2 mL of acid to our solution”, but rather “2 mL of dilute HCl was measured in a 10 mL graduated cylinder and added to the solution in the 250 mL beaker.” Or, in our plant investigation above, you might write “A geranium plant was placed in a sunny window and the temperature was recorded using an alcohol thermometer. The number of hours of exposure to sunlight was measured using a timer and recorded on a daily basis.” Notice that you have not only explained the steps taken but also indicated the equipment necessary at the same time.

Results

In this section you state your results (Shocking!). Do not make any comments about the results in this section - simply report the data and any observations. Both quantitative (measured values) and qualitative (observed characteristics) are included. Try to choose a format that makes the data easy for the reader to interpret. You might use tables, charts or graphs. Include a descriptive title and a separate number for each so they can be referred to in the text of your Discussion section. Each table or figure should be self-explanatory; the reader should be able to understand each without referring to the written text. Keep titles simple and to the point. Remember that you must show your raw data (i.e., what you actually observed or recorded) as well as the results of any calculations. Imagine that you are answering the questions “What did you find?” or “what did you see or measure?” The results section should summarize the data and observations from your investigations without discussing their implications.

Note: The terms “Drawing” or “Graph” are not used in formal reports. Only use Figure (for drawings, diagrams, flow-charts, graphs, etc.) or Table (for data tables).

All results must be fully described. Presentation of data (figures or tables) without adequate description, in words, is inadequate and incorrect. Present only what was actually observed or obtained in the investigation and not what should have occurred. If calculations are necessary, include an example.

The most common error is to begin discussion of the results (i.e., discussing their implications) in this section. For example, consider these sentences:

1. A leaf from the “sunny” plant was observed to contain starch

2. A leaf from the “sunny” plant was observed to contain starch because it was exposed to sunlight.

The first sentence belongs in the Results section as it describes an observation (the presence of starch). The second sentence belongs in the Discussion section as it describes an observation (the presence of starch) and interprets this information (gives a reason).

Discussion

The discussion is perhaps the most important part of your lab report - but often the most challenging. This is where you provide an interpretation or explanation of your results. Do not simply restate your results - you already did that in the results section. You must discuss what they mean and why they are important. Discuss what you were able to learn from your results. In this section the author (you) is expected to analyze and interpret the investigational data relative to the objectives described in the Introduction.

If the investigation appears to have gone well and you find results that you were expecting (i.e., agree with generally accepted or expected values), you need to interpret those results. This means that you explain for the reader what your results mean. If you find some unexpected results, you face the difficulty of explaining those results. In other words, you must provide a possible explanation as to why you did not find what you had expected to find. Don’t worry if your results seem strange - discuss the results you got. Remember, a great deal of science comes from finding the unexpected.

Attempt to present the concepts or relationships shown by the results but do not repeat the results more than absolutely necessary. Attempt to explain the theoretical basis for your results (e.g., reaction mechanisms for stains, or role of sunlight in photosynthesis) where possible. Compare your results with information found in reference materials (textbooks, websites, etc.). If questions are provided for the lab, they are meant to be a guide to help you write a complete discussion. Do no limit your Discussion to only answering the questions.

A good discussion section should do each of the following:

1. Discuss the results, that is, present relationships, principles and generalizations.

2. Point out exceptions and lack of correlations; state unsettled points.

3. State how the results relate to the existing knowledge. All investigational results must be addressed, whether they agree or disagree with the literature.

4. State the significance and implications of the data. What do the results mean?

5. Avoid using words like “relative,” “huge,” “unbelievable”, “tiny,” “massive,” “fairly,” etc. These words don’t hold any concrete meaning so should be avoided.