Writing the Discussion Section
The Discussion should be written after the Results section so that you have a good idea of what the experiment has demonstrated. The discussion section should definitely have a statement of your expected findings (Pechenik, 86). This should include your hypothesis and a brief statement about why these types of results are expected. There should also be a comparison of how your actual results related to your expected findings (Pechenik, 86). Here, you should state whether or not your results supported or didn't support your hypothesis. In addition, the degree to which the evidence supported your hypothesis should be stated. For example, were the results completely supportive, or were there variances?
There should be an explanation of unexpected results (Pechenik, 86). When looking for possible explanations, consider the following:
A common mistake that many writers make is to blame themselves for the unexpected results. Unless you actually made a mistake following the methods of the experiment, and could not go back and correct it, do not make up such errors to explain the variances you observe. Think about and analyze the methods and equipment you used. Could something different have been done to obtain better results? Another possibility to consider is if the experiment was conducted under factors that were considerably different from those described in the manual. Be sure to include ideas on how to test these explanations (Pechenik, 86). Briefly explain a way to test these possible reasons for unexpected results. For example, if there is a problem with the methods, maybe the experiment should be reproduced with an added step. Also, mention what kinds of experiments still need to be conducted in order to obtain more information.
The following text includes two samples of discussion sections of a lab report on enzymes. Italicized words are links to explanations of why that particular part of the introduction is important and what makes the sentences appropriate or in need of improvement.
Explanations of the Example Links
Results: This author does a good job of answering the questions that should be addressed in a discussion. For example, in the very first sentence he stated what he expected to find and also whether or not the results he obtained supported or failed to support his hypothesis. This is a good, strong way to start a discussion section. It starts off with the facts of the experiment and then later on, the author can move on to his opinions. (return to Sample 1)
Absorbance: A good discussion includes good ideas and also exact and detailed support of these ideas. In addition to starting off well, the author also goes on to explain the specific results of the experiment that support his hypothesis. This is what defines the strength of his discussion section. (return to Sample 1)
Explanation: After his explanation he presents the unexpected results and discusses possible reasons for this data. The author's explanation of possible reasons for unexpected results is good because it shows that he thought about the problems. He does not blame himself for the unexpected. Instead, he considers the methods used, presents a possible explanation, and then justifies his ideas. (return to Sample 1)
Catalyze: This author does a good job outlining his discussion; however, he is lacking the specifics to make a good discussion. The first two sentences are better placed in the introduction. However, he does state his expectations and whether or not his results supported these expectations. He could have made this part better by stating this more authoritatively, for example: "It was expected," and not, "It would be expected that." (return to Sample 2)
Unexpected results: The biggest problem this author had was explaining the unexpected results. He blamed himself, saying he read the equipment wrong and passed off the unexpected results as human error. (return to Sample 2)
Enzymes: This author does not develop his argument enough. One example of this is the affects harsh environmental factors have on enzymes. He could have stated how the acidity caused the enzymes to denature, thus creating less efficiency. (return to Sample 2)
All citations from Pechenik, Jan A. A short guide to writing about Biology. pp. 54-102, Tufts University: Harper Collins College Publishers. 1993.