How to Write a Lab Report

    Learning to write effective laboratory reports is an important skill regardless of what career path you choose to pursue.  Writing these reports develops the ability to organize ideas logically, think clearly, and express yourself accurately and concisely. 

    Your lab report will be partitioned into five sections just like a journal article.  You will have an
abstract, an
introduction,
methods,
results, and a
discussion.  Just because there are all those sections does not mean that it has to be very, very long.  It just needs to be complete.  In addition, there are some overriding format rules for you to follow.  These rules are listed at the bottom of this page.

    Here’s what needs to go into each major section of the report:

Abstract:

    This may be hard to write first… if so, skip it, and start writing on the results section.  Come back to writing this last.

    The abstract is an overall summary of what you did and why.  It is short (typically less than 250 words).  It usually includes a sentence on each of the other sections of the paper.  Therefore, the basic format of an abstract is:

1. State the principle objectives and scope of the investigation.

2. Describe the methodology employed.

3. Summarize the results.

4. State the principle conclusions.

For example, in a study of crop pests, you might write something like…

    “Over the past 5 years, farmers in Western Massachusetts have noticed an increase in damage to specific crops, but have been unable to pinpoint the cause for this damage. In this study, a detailed examination of those crops was carried out to determine the specific cause of the damage. We found that the damage was due to a specific beetle, which kills the crops by eating the leaves of the crop plants. We have proposed that the reason why this beetle is causing more damage in Western Massachusetts than in other areas is because of the especially rainy seasons in the past few years combined with the high altitude in the Berkshires.”

    Although this fake abstract is vague (because there’s no such beetle problem), the general flow of an abstract, approximately one sentence summarizing each section, should be clear.  Some students and authors feel a desire not to give it all away in the abstract, like saving a punch line for the end.  However, it is preferable for you tell it all because then your paper is more understandable.  This fake abstract is certainly long enough, and notice that it is primarily written in past tense.

Introduction:

    This section explains
why you did what you did. It gives the reader an understanding of the
rationale for the study or experiment. In order to tell someone why you’re doing something, it usually requires a bit of
background information.  Finally, the end of the introduction usually also includes a
very brief statement about what the results of the study showed.  The entire introduction is not usually short– it is rather meaty.  Here is an example of what an introduction is for, but not an entire introduction, because then it would be long:

    If you saw me with a wrench under a sink during lab, my telling you that I’m trying to fix sink leaks would probably not be enough information. You’d want to know why I was doing it (and not teaching), rather than someone who is a trained plumber. You’d also want to know what kind of a leak it was, so that you could understand if it was an urgent repair. You’d even have to already know what a sink was and what pipes and leaks were.

Therefore, the general rules for the introduction are:

1. It should present, with clarity, the nature and scope of the problem investigated.

2. It should review the pertinent literature (sometimes, in our cases, just the lab handout) to orient the reader to the subject and methods used.

3. It should state the principle results and conclusions of the investigation.

    So when you go about trying to write an introduction for an experiment that we did in lab, you will need to tell me why doing that experiment was important (what was the goal?), some background about the type of work you were doing, and what you found out.

Methods:

    This section is where you write a thorough description of how you actually performed the experiments of your investigation.  It should be specific enough to be followed by another researcher, but not too detailed; how to create a balance between enough information but not too much is a tricky one to learn. 
This is a good place to start writing your lab report… you don’t even have to have all the results in before you get started.

    You will receive lab handouts for each lab that contain the methods and materials we will use. Those are exceedingly detailed methods (as much detail as I can stand to write!), with information specific to a beginner in that technique.  That is not what is expected in the methods section of your lab report.  While it is true that someone should be able to repeat your study based on reading your methods section, that particular someone would be expected to know all the basic, beginner information about the techniques—so although you are learning that information in your lab, you do not have to write it all down.  You just have to figure out which information is pertinent (that’s the tough part).

    For example, you learned how to align your specimen in the paraffin block on the microtome in order to cut it properly, but you certainly do not have to describe that in your methods section… just saying that you sectioned your block on a microtome would explain all of that. You would, however, need to give some details, like the thickness of the sections, so that your reader could understand the data.

    About the format for the methods section.  There is no real way to write this section so that it reads like prose.  It won’t sound beautiful or flow perfectly, but it should still be written in paragraph form.  Keep in mind that this section does not need to be exceedingly long (and no
separate materials list should be included).  Finally, if you were using multiple new techniques, you might find it simplest to have subheadings within this section for each technique.

Results:

    Here’s where you tell the reader what you saw, but not what you think about what you saw.  It should include figures and/or tables of data.  These figures and tables should be numbered and titled.  In the text of the results section you will simply clarify your quantitative or diagrammatic data in
words for the reader to understand.  Be sure to refer to your figures and/or tables in the text of this section.  If I continue the crop pest example,

    “37% of all plants showed evidence of beetle damage.  Because beetle damage ranged from barely detectable in some plants to extreme in others, we came up with a classification system for it. If beetle damage killed the plant, we categorized it as “severe.”  When it was found on more than 50% of the leaves we categorized it as “extensive,” while if it was found on more than 20% but less than 50% of the leaves we called it “moderate.”  Finally, if it was on under 20% of the leaves, we categorized it as “minimal.”  Table #1 shows the percentage of damaged plants in each category.  It should be noted that the greatest number of damaged plants were at the extremes, either severe or minimal.”

    You would then have to resist the urge to explain why severe and minimal damage were seen the most, because that is an interpretation of your results—save that for the discussion section.

    Please note that when describing your data, it is essential to first remind the reader what the experiment was.  So, an overall description of each experiment should be included for each section of data– but do not repeat the experimental details provided in Materials and Methods.

A few word of wisdom from others:

Discussion:

    This section is where you can give the reader your opinions based on the evidence (but keep in mind that opinions that go beyond the evidence are NOT welcome here… we need to remain scientific, not philosophical).

This section (in a lab report) should include the following components:

1. The principles, relationships and generalizations shown by the results.  Basically, turn the individual results into a whole story.

2. Point out any exceptions or any lack of correlation with expected results.  Never try to fudge data that doesn’t quite fit.

3. Conclusions based on results should be written as clearly as possible, summarizing your evidence for each conclusion.

4. Don’t be shy; discuss any practical applications of your results or methods.

5. Identification of the next step of your investigation or what you would do differently if you could repeat your experiments.  For example, what study might you do based on what you figured out, or that you might increase the amount of substrate you used if you could do it again.

Back to the crop pest example:

    Based on the data which showed that plants seemed to either be eaten up entirely or ignored, it seems as if once a beetle stops at a plant, it stays there until it is done with the plant rather than jumping around from plant to plant.  Observation of beetle behavior would be necessary to investigate this particular possibility further.

    One last comment about the discussion section that might help you as you write your report:  Your verb tense will swing back and forth between present and past tense.  Your own results should be reported in the past tense.  Ideas about the meaning of these results would be reported in the present tense.

Formatting Details:

Hint:

    Sometimes it is easiest to write the report in the following order (but put them in the right order to turn it in):  methods, results, introduction, discussion, abstract.

Guide was written by Dawn Tamarkin, Ph.D for Bio 351 at STCC.

Used with permission

Rubric For Lab Report

Lab report guidelines -Adapted from Lisa Rapp’s Biotechnology Program at STCC.