Discussion

Purpose

The main purpose of the discussion is to interpret and evaluate your results to give them meaning. While your results, like a photograph, are a permanent record of your observations, the meaning of your results (i.e. interpretations) may change over time to reflect changes in scientific knowledge. However, it is also important to offer some original ideas and interpretations in your discussion.

What to include

A complete interpretation addresses these four key tasks:

1. clearly answers the central question(s) posed in the introduction,
2. notes and discusses interesting or unexpected findings (what might they mean biologically),
3. relates results to the general understanding of the field, and
4. makes meaningful suggestions for further studies.

Strategy

There is no single strategy that will work for all discussions. The approach you take will be partly dictated by how you laid out the results. Your lab instructor will probably offer some tips specific to the report you are working on, but we have included some strategies here that should be helpful in addressing the four goals listed above.

Clearly answer the central question(s) posed in the introduction.

This should be done right at the beginning of your Discussion. One way to do this is to clearly state your conclusion and then back it up with the evidence that you presented in the Results (but make sure you are not simply repeating the results). Make sure your conclusion clearly addresses the purpose given in the Introduction. For example, if your purpose was to answer a specific question (Why is the sky blue?), then your conclusion should clearly answer that question (The sky is blue because…).

Note and discuss interesting or unexpected findings.

Frequently our results do not just answer the question we asked, but tell us more than we expected. If you noticed some interesting trends when analyzing your results, don't ignore them, rather point them out and discuss what they might mean. Don't simply write them off as 'novice mistakes'. Unexpected results can be the most interesting part of your report. Remember, the majority of important scientific discoveries were made when we were looking for something else.

Relate your results to the general understanding in the relevant field.

For a reader to completely appreciate your results and conclusions, you must clearly point out how your results extend current knowledge and how they compare to previously published results. For example, if you find a published study that is similar to some aspect of your study, compare and contrast your results to these previously published results. If your results are different from what someone else found don't assume your results are wrong; instead, try to explain why the results are different. Frequently, when you look carefully, you can find differences in the studies' methods that may account for the conflicting results. For example, if you conducted enzyme assays at a slightly lower temperature than was used in other situations, and this completely altered the trend, your results might be very important for understanding how that enzyme works. This is the place to speculate. Caveat: Make sure you clearly indicate what is speculation.

Explaining a contrasting result

The Michaelis constant in our experiment was two-fold lower than found previously (some citation). This could be (The phrase "could be" alerts the reader that you are making a speculation.) because our experiments used a lower temperature that is closer to the temperature this enzyme would normally function at.

Also, consider how your results might extend general biological understanding. In biology, we are always striving to better understand how life works. While your stated purpose should be specific, it should also fit in with some aspect of understanding life. For example, maybe you were conducting a genetic study to understand how a particular trait is inherited. Based on how the trait is inherited, can you speculate as to how the trait is determined at a molecular level?

Note that you should not be adding new background information here.

Make meaningful suggestions for further studies.

All good studies lead to more questions, and by the time we finish one study, we are usually full of ideas for the next logical step in our quest to understand a particular system. Share at least one of your good ideas with your reader. After all, you want your audience to watch for and read your next story.

Where do meaningful suggestions come from?

• If you have found a reasonable explanation for why your results are inconsistent with results from another study, suggest a further study that could test if your explanation is correct.
• If you found something you were not expecting, what would be the next logical step in exploring this unexpected observation?
• If your study produced negative results, suggest how you could modify the study to produce more interesting results.

The key word here is MEANINGFUL. Any suggestion you make should:

• logically follow what you did (i.e. "repeating the experiments in space" is usually not the logical next step)
• be doable with scientific tools and strategies you know exist (i.e. don't suggest a study that would require equipment or techniques that do not exist)
• have a reasonable chance of yielding NEW knowledge (i.e. simply repeating the experiment with a larger sample size, but with no meaningful changes, will not likely lead to new knowledge)

Make sure you have clearly explained how the suggested study meets these requirements. Don't leave your reader to guess why changing the temperature of the experiment is a good idea.

Also consider

You may discuss sources of error in the experiment, but assume that your results reflect reality. Students often feel that their discussion should consist mainly of an analysis of all the things that went wrong with the experiment. Naturally, all experiments have some weaknesses, but for the purposes of this exercise assume that your results are reasonable. It is okay to get negative results. You should, however, suggest additional experiments using modified methods.