Focused scientific motivation for your study
A clearly focused scientific motivation is the critical starting point for any field research project. In all cases, your motivation should be stated in the form of a question or hypothesis that addresses a possible relationship between variables. In some cases, your study may be motivated by a set of related questions and/or hypotheses.
Dependent and independent variables
The dependent variable is the one you’re interested in explaining — for example, variation in the amount of leaf damage to sugar maple trees caused by insects.
Independent variables are factors that might influence the dependent variable.
Some possible independent variables that could affect the dependent variable 'leaf damage' are tree genotype, amount of nutrients in the soil, and tree height.
Often it’s helpful to list your variables of interest first, then, figure out specific questions or hypotheses addressing possible relationships between those variables (see example here).
In order to help you get started, see the questions below. Also, see these tips about whether to choose a question or hypothesis as your scientific motivation.
Questions to ask yourself
If you're stuck trying to shape your preliminary ideas into a focused question or hypothesis, try asking yourself each of these questions. If the answer is yes, try exploring the tips.
Are you unsure of how to narrow your focus, you just know of a specific organism, habitat type, ecosystem, or even an abiotic factor that interests you? If YES, try these tips for a preliminary investigation.
Tips for a preliminary investigation
If you're simply starting with some organism, habitat, ecosystem or abiotic factor of interest, it might be most appropriate for you to conduct a preliminary investigation motivated by a question. See if one of the following approaches or example questions works for you.
Several Approaches:
Investigating variation with an environmental factor—
How does the abundance of (insert your organism of interest) vary with (insert an environmental variable that you think might be appropriate)? For example, how does the abundance of Cinnamon Fern vary with soil moisture? In this case, the abundance of Cinnamon Fern is the dependent variable and soil moisture is the independent variable.
Comparing abundance in different habitats or ecosystem types—
Is the abundance of (insert your organism of interest, or tweak wording and insert an abiotic facture) affected by (insert what you are comparing). For example, is the abundance of porcupine affected by forest type? (In this case, abundance of porcupine is the dependent variable and forest type is the independent variable.) Here, you may need to focus even more, such as choosing two specific forest types to compare.
Documenting a pattern of distribution within an area where organism occurs—
Within a specific habitat patch (you would need to specify) where is (insert organism of interest) most abundant? For example, on Sugar Maple trees, where in the canopy are spindle gall mites most abundant? In this case, you would then need to further specify what canopy factors (independent variables) to include, such as canopy height, canopy edge vs. interior, distance along branch out from tree, etc.
If you choose one of the approaches listed above, you will be exploring a possible pattern in nature. This exploration can be thought of as working on Step I of the Scientific Method: Observation. Your results may well lead to Step II: Generating hypotheses.
RECOMMENDED: Run your question by your professor or advisor - science is a collaborative process. Professional scientists share and refine ideas to get them right . . . clearly it makes sense for students and professors to do the same! Also, in some cases, hypothesis testing may be required for your project, so you might need to do some more refining of your ideas.
(Back to Questions to Ask Yourself)Tips for a follow-up study
There are many possible ways to follow up a study that has already been conducted.
If the results from the first study are preliminary, but not very conclusive, it might be appropriate to simply repeat the original study with little or no modification.
In some cases, it might make sense to repeat the study, but use a much larger sample size. After all, you should have extra time and effort available since you didn't have to come up with the project from scratch!
If the results from the first study tested the effect of one independent variable on an organism (such as the effect of tree aspect [North vs. South] on suitability for bat roosting sites), maybe you can choose another independent variable to test (such as tree height).
RECOMMENDED: Run your ideas by your professor - make sure your study is sufficiently different from the original study!
(Back to Questions to Ask Yourself)Tips for exploring relationships between variables
If you have several variables in mind to test, great, you potentially have a lot to work with! A useful first step is to figure out what your dependent variable is. The dependent variable is the one that you are trying to explain, the one that might be influenced by the independent variable(s).
Making a list of possible dependent variables and independent variables can be a great way to focus your interests and turn your ideas into a specific question or hypothesis. The following simple example might help to clarify.
Imagine you're interested in studying crayfish. An approach for beginning would be to list variables you can reasonably measure (admittedly, some in this example list could be tricky to measure):
Now, list the dependent variable (what you are trying to explain that might be influenced by the other variables):
And here are the independent variables that might influence crayfish abundance:
You should be able to come up with at least four specific questions and possibly four specific hypotheses.
For substrate type, here's an example question:
Does crayfish abundance vary with substrate type (rocky vs. sandy)?
And here's an example hypothesis:
In Pearly Pond, crayfish abundance is greater in areas with sandy substrate than areas with rocky substrate.
RECOMMENDED: Run your ideas by your professor. In some cases, you may be required to test hypotheses, so the question approach may not be appropriate. Also, it's great to get input and make sure you aren't confusing your variables!
(Back to Questions to Ask Yourself)Which to choose, question or hypothesis?
If you have little or no preliminary information and really have no reason to make a specific prediction (but have reason to suspect you're investigating relevant variables), a question might be most appropriate. One way to think of your study is that you're working on Step I of the Scientific Method: Observation. Your focused observation and data collection guided by your question may lead to a specific hypothesis to test. On the other hand, if you have preliminary information based on observations or based on other studies about how the independent variable might influence the dependent variable, go with an hypothesis.
