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Biology Department Writing Guide
Methods
Function: In this section you explain clearly how you carried out your study in the following general structure and organization (details follow below):
- the subjects used (plant, animal, human, etc.) and their pre-experiment handling and care, and when and where the study was carried out (if location and time are important factors)
- if a field study, a description of the study site, including the physical and biological features, and precise location;
- the experimental OR sampling design (i.e., how the experiment or study was structured. For example, controls, treatments, the variable(s) measured, how many samples were collected, replication, etc.)
- the protocol for collecting data, i.e., how the experimental procedures were carried out
- how the data were analyzed (statistical procedures used)
Organize your presentation so your reader will understand the logical flow of the experiment(s); subheadings work well for this purpose. Each experiment or procedure should be presented as a unit, even if it was broken up over time. In general, provide enough quantitative detail (how much, how long, when, etc.) about your experimental protocol such that other scientists could reproduce your experiments. You should also indicate the statistical procedures used to analyze your results, including the probability level at which you determined significance (usually at 0.05 probability).
Style: The style in this section should read as if you were verbally describing the conduct of the experiment. You may use the active voice to a certain extent, although this section requires more use of third person, passive constructions than others. Avoid use of the first person in this section. Remember to use the past tense throughout. The Methods section is not a step-by-step, directive, protocol as you might see in your lab manual.
Strategy for writing the Methods section.
Describe the organism(s) used in the study. This includes giving the source (supplier or where and how collected), size, how they were handled before the experiment, what they were fed, etc. In genetics studies include the strains or genetic stocks used.
Describe the site where your field study was conducted. The description must include both physical and biological characteristics of the site pertinant to the study aims. Include the date(s) of the study (e.g., 10-15 April 1994) and the exact location of the study area. Location data must be as precise as possible: "Grover Nature Preserve, " mi SW Grover, Maine" rather than" Grover Nature Preserve" or " Grover". When possible, give the actual latitude and longitude position of the site (the WWW has sites which provide this service). It is most often a good idea to include a map (labeled as a Figure) showing the location in relation to some larger more recognizable geographic area. Someone else should be able to go to the exact location of your study if they want to repeat or check your work, or just visit your study area.
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NOTE: For laboratory studies you should not report the date and location of the study UNLESS it is relevant. Most often it is not.
Describe your experimental design clearly. Be sure to include the hypotheses you tested, controls, treatments, variables measured, how many replicates you had, what you actually measured, what form the data take, etc. Always identify treatments by the variable or treatment name, NOT by an ambiguous, generic name or number (e.g., use "2.5% saline" rather than "test 1".) When your paper includes more than one experiment, use subheadings to help organize your presentation by experiment. A general experimental design worksheet is available to help plan your experiments in the core courses.
Describe the protocol for your study in sufficient detail that other scientists could repeat your work to verify your findings. Foremost in your description should be the "quantitative" aspects of your study - the masses, volumes, incubation times, concentrations, etc., that another scientist needs in order to duplicate your experiment. When using standard lab or field methods and instrumentation, it is not always necessary to explain the procedures (e.g., serial dilution) or equipment used (e.g., autopipetter) since other scientists will likely be familiar with them already. You may want to identify certain types of equipment by brand or category (e.g., ultracentrifuge vs. prep centrifuge). It is appropriate to give the source for reagents used parenthetically, e.g., "....poly-l-Lysine (Sigma #1309)." When using a method described in another published source, you can save time and words by referring to it and providing the relevant citation to the source. Always make sure to describe any modifications you have made of a standard or published method.
Describe how the data were summarized and analyzed. Here you will indicate what types of data summaries and analyses were employed to answer each of the questions or hypotheses tested.
The information should include:
- how the data were summarized (Means, percent, etc) and how you are reporting measures of variability (SD,SEM, etc)
- this lets you avoid having to repeatedly indicate you are using mean ± SD.
- data transformation (e.g., to normalize or equalize variances)
- statistical tests used with reference to the particular questions they address, e.g.:
- "A t-test was used to compare mean flight duration before and after applying stablizers to the glider's wings."
- "One way ANOVA was used to compare mean weight gain in weight-matched calves fed the three different rations."
- any other numerical or graphical techniques used to analyze the data
Here is some additional advice on particular problems common to new scientific writers.
Problem 1: The Methods section is prone to being wordy or overly detailed.
Avoid repeatedly using a single sentence to relate a single action; this results in very lengthy, wordy passages. A related sequence of actions can be combined into one sentence to improve clarity and readability:
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Problematic Example: This is a very long and wordy description of a common, simple procedure. It is characterized by single actions per sentence and lots of unnecessary details.
"The petri dish was placed on the turntable. The lid was then raised slightly. An inoculating loop was used to transfer culture to the agar surface. The turntable was rotated 90 degrees by hand. The loop was moved lightly back and forth over the agar to spread the culture. The bacteria were then incubated at 37 C for 24 hr."
Improved Example: Same actions, but all the important information is given in a single, concise sentence. Note that superfluous detail and otherwise obvious information has been deleted while important missing information was added.
"Each plate was placed on a turntable and streaked at opposing angles with fresh overnight E. coli culture using an inoculating loop. The bacteria were then incubated at 37 C for 24 hr."
Best: Here the author assumes the reader has basic knowledge of microbiological techniques and has deleted other superfluous information. The two sentences have been combined because they are related actions.
"Each plate was streaked with fresh overnight E. coli culture and incubated at 37 C for 24 hr."
Problem 2: Avoid using ambiguous terms to identify controls or treatments, or other study parameters that require specific identifiers to be clearly understood. Designators such as Tube 1, Tube 2, or Site 1 and Site 2 are completely meaningless out of context and difficult to follow in context.
Problematic example: In this example the reader will have no clue as to what the various tubes represent without having to constantly refer back to some previous point in the Methods.
"A Spec 20 was used to measure A600 of Tubes 1,2, and 3 immediately after chloroplasts were added (Time 0) and every 2 min. thereafter until the DCIP was completely reduced. Tube 4's A600 was measured only at Time 0 and at the end of the experiment."
Improved example: Notice how the substitution (in red) of treatment and control identifiers clarifies the passage both in the context of the paper, and if taken out of context.
"A Spec 20 was used to measure A600 of the reaction mixtures exposed to light intensities of 1500, 750, and 350 uE/m2/sec immediately after chloroplasts were added (Time 0) and every 2 min. thereafter until the DCIP was completely reduced. The A600 of the no light control was measured only at Time 0 and at the end of the experiment."