SelfGuide

Printable Version


SECTION FOUR : Discussion

Interpreting the results of the lab

Step 1: Write a sentence or two stating whether or not the results from the lab procedure fully support your hypothesis, do not support the hypothesis, or support the hypothesis but with certain exceptions.

More Help:

Experimental science is all about testing hypotheses. Thus, the statement of whether or not your hypothesis has been supported is critically important to the lab report. It is by no means a failure if your data do not support your hypothesis; in fact, that can be more interesting than the other way around, because you may find a new perspective for looking at the data. Failure to support hypotheses is common in science, and often serves as a starting point for new experiments.

  • Go back to the statement of hypothesis in the Introduction. Then review your findings, the data from the experiment. Make a judgment about whether or not the hypothesis has been supported. It is at this point that you, as a scientist, must be as unbiased and objective as possible.
  • Write a statement stating your judgment. There are three possible judgments you can make:
    1. the data support the hypothesis;
    2. the data do not support the hypothesis; or
    3. the data generally support the hypothesis but with certain exceptions (tell what those exceptions are).

Example: "The hypothesis that X solution would increase in viscosity when solutions Y and Z were added was supported by the data."

Step 2: In a paragraph, identify specific data from your lab that led you to either support or reject your hypothesis. Refer to the visual representations of your data as evidence to back up your judgment about the hypothesis.

More Help:

It is important to back up the statement about the hypothesis with direct evidence from the lab data that support, do not support, or partially support the hypothesis.

  • Return to the Results to identify the particular data that led you to your judgment about the hypothesis.
  • Write a paragraph (or 2 if necessary) in which you present the relevant pieces of data from the lab and show how they relate to the hypothesis.
  • Refer to data from specific visuals appropriately: Table 1, Figure 2, etc.

Step 3: In a paragraph, use your understanding of the scientific concept of this lab to explain why the results did or did not support your hypothesis. If the hypothesis from the Introduction was not fully supported, show how your understanding of the scientific concept has changed. Note any citations you use here for including in the Reference section of your report.

More Help:

In Step 2 you pointed to data that led you to your judgment about your hypothesis. Now you use your understanding of the scientific concept of the lab to explain your judgment. Whatever the relationship between the hypothesis and the results, you must provide a logical, scientific basis for it.

  • Return to the scientific reasoning you used to generate your hypothesis (at the end of the Introduction). Use it and your understanding of the scientific concept of the lab as starting points for your explanation. Your explanation is likely to follow one of four scenarios. Choose the one that best fits your report:
    • If the results fully support your hypothesis and your reasoning in the Introduction were basically sound, then elaborate on your reasoning by showing how the science behind the experiment provides an explanation for the results.
    • If the results fully support your hypothesis but your reasoning in Introduction was not completely sound, then explain why the initial reasoning was not correct and provide a better reasoning.
    • If the results generally support the hypothesis but in a limited way, then describe those limitations (if you have not already done so) and use your reasoning as a basis for discussing why those limitations exist.
    • If the results do not support your hypothesis, then explain why not; consider (1) problems with your understanding of the lab's scientific concept; (2) problems with your reasoning, and/or (3) problems with the laboratory procedure itself (if there are problems of reliability with the lab data or if you made any changes in the lab procedure, discuss these in detail, showing specifically how they could have affected the results and how the uncertainties could have been eliminated).

Step 4: Discuss other items as appropriate, such as (1) any problems that occurred or sources of uncertainty (see below for definition of underlined word) in your lab procedure that may account for any unexpected results; (2) how your findings compare to the findings of other students in the lab and an explanation for any differences; (3) suggestions for improving the lab.

Sources of Uncertainty:

In science, a source of uncertainty is anything that occurs in the laboratory that could lead to uncertainty in your results. Sources of uncertainty can occur at any point in the lab, from setting up the lab to analyzing data, and they can vary from lab to lab. This is why it is so important to keep detailed notes of everything you do in the lab procedure and any problems you encounter. Try to be especially aware of any problems in setting up the lab, calibrating instruments, and taking measurements as well as problems with the materials you are using.

More Help:

After dealing with the critical issue of the hypothesis, the rest of the Discussion may consider other issues. You can address these in separate paragraphs.

  • Return to the notes you took during the lab procedure. Look for possible sources of uncertainty in setting up the lab, calibrating instruments, and taking measurements as well as problems with materials you are using.
  • In scientific articles, the Discussion is where scientists typically compare their results to those from other scientific experiments. You can do something similar by comparing your results to those of other students in the lab. In your paragraph, comment on any similarities or differences you find and offer possible explanations for the differences. Be sure to check with the lab instructor to see if it is permissible to compare results.
  • Professors who write lab manuals are typically interested in how they can improve the experiments in the manuals. You can also demonstrate your ability to provide productive critique of the lab by offering suggestions for improvement.

    For advanced labs:

  • It may be useful to classify the kinds of uncertainty you have identified. Sources of uncertainty can be classified as random--those that cannot be predicted--or as systematic--those that are related to personal uncertainty, procedural uncertainty, or instrumental uncertainty.

 

 

 

 

 
 
 

© Copyright NC State University 2004
Sponsored and funded by National Science Foundation
(DUE-9950405 and DUE-0231086)

Site design by Rosa Wallace

Rev. RW 5/16/05