This activity is primarily a brainstorming activity that looks at the assumptions, mechanisms, and unanswered questions that are buried in the students’ picture of the system they are studying. Ultimately, individuals or groups of students will come up with one or more questions and will choose one to turn it into a hypothesis. They will then propose a general approach for a research project that addresses their hypothesis.
Background for Teachers
Developing hypotheses is a process of refinement. Students should start with reviewing whet they know about their system, observations they have made, and then posing as many “I wonder” and “I think” types of questions as they can. Some questions may lead to dead ends; some will not, and these ones are the only way to get to hypotheses.
We suspect that a lot of the trouble that students have is in moving from a very general kind of question ("How does this system work?") to the more specific kind of assertion that makes for a hypothesis. What may be missing is the model.
Have your students refer to diagrams of their system, observations they may have made, or the Table of Field Variables. These all inform a system model, based on information the students have already gathered and it will help them with their thinking. The model is what generates some hypotheses. With a model, the students can ask, “If this is the model, then what would we expect to see?”, "If these things are related, how would one affect the other?" The hypotheses grow out of following out the implications of the model.
Additional information that students can use to construct their model of how the system works: additional reading or understanding about the other abiotic and biotic factors in the system that they are studying. The key thing is to have the students try to draw a picture of how the system works with regard to their questions. When there is a part of that picture that is fuzzy or that they don’t understand, they need to do some more reading, or—devise an experiment to find out what they need to know.
Note, by the way, that the model that the students come up with does not have to be TRUE in some final sense. It just needs to hold together, be internally consistent, make sense, and serve as a good foundation for their continued thinking and research.
What kinds of data can the students collect?
It may be difficult for the students to develop questions because they do not know what kinds of information are available to them. What the students can measure depends on the types of resources that are available. Use the “Table of Field Variables” to provide them with the kinds of things that they can collect and measure in the system that you are studying.
Keep in mind: You andf the students will have access to all of the data from all of the sites sampled by many schools.
What kinds of questions can the students explore?
For most students you will need to guide them from having a general area of interest toward having a question that can be answered with data. Keep in mind that the students will be able to explore two general kinds of questions:
Questions about differences:
Does one set of conditions contain, on average, more than some other set? Or does one set of conditions change the variability more than some other set? There are many questions of this kind. These kinds of questions will involve a comparison of means, or averages, and looking at variability.
Questions about the strength of relationships:
What goes with what? IWhat is the relationship between the dominant tree type and stream nitrogen concentration? Is there a strong relationship between the girth of the trees in a watershed and the depth of snowpack? These kinds of questions involve creating a scatter plot to see if there is an orderly relationship between the two factors. Of course, it requires that each factor be something that can be expressed in a numeric relationship on the scale of the axis of a graph. Time, size, age, and other “countable” factors work well for this. Something that does not fit into an interval scale or ratio scale won’t work (for example: conifer trees versus deciduous trees). Help the students be clear about which kind of question they are asking-use the Graph Choice Chart to help the students. This will be very useful as they think through the design of their experiment.
Our experience has been that questions about relationships often open up richer opportunities for learning than simple questions about differences. Looking at how much two factors are correlated is a good way to get a better understanding of what is happening in a system. Questions about differences are useful too, of course, and provide important insights into the structure of a system. But, if students are looking at an issue that can be explored through a scatter plot, encourage them to pursue that direction.
Dr. Kevin Simon, Department of Environmental Sciences, University of Auckland, Auckland, New Zealand, gave some feedback on a class’ hypotheses and his comments might help you in the development of your students’ hypotheses:
A hypothesis that explains something leads to more interesting and informative research. Hypotheses that use the words “because” or “due to” or “cause” are generally more informative. See the examples below:
Hypothesis #1—There will be fewer invertebrates in streams subject to frequent floods than in streams that experience less frequent flooding. You might sample and, indeed, decide that this is so. However, you don’t know WHY.
Hypothesis #2—There will be fewer invertebrates in streams subject to frequent floods BECAUSE the stream is highly disturbed, causing high insect mortality.
This 2nd hypothesis now explains something and it leads to specific predictions that you can test.
There is no Right; there is no Wrong
Once each group has identified a question - for example, "Does tree type affect mercury in stream invertebrates?" - have students turn the question into a hypothesis by expressing it as an assertion, a claim. That means choosing one outcome over the other, based on what the model suggests. It is important to assure the students that a hypothesis is a well-reasoned prediction from the model and that there is no right or wrong. Scientists don't use the word "wrong" (or "right", for that matter) when discussing hypotheses, or results. For example, in the question about nitrogen in different watersheds, a working hypothesis might be something like, "If nitrogen is used differently by different tree types, then watersheds with different dominant tree types will have different concentrations of nitrogen in the stream water, because the trees will make different demands on the nitrogen available. ”
It is conceivable that students have a hypothesis that does not involveexactly what is being studied by the research scientist (e.g., is there a relationship between amount of canopy cover and air temperature at ground level?). This is all right with the project if it supports your learning objectives.
- That not all questions are testable
- That hypotheses require an understanding of a system or model
- That data are needed to determine the strength of the hypothesis
- Students develop testable questions, a hypothesis, a hypothetical graphs and “shopping list” of the type(s) of data they need to support their hypothesis and shed light on the question
Where does this lesson happen in the Project?
This is the first lesson in Unit 3: Developing Questions and Hypotheses. It should follow Units 1 and 2 (both on developing background understanding).
Make sure your students have any system diagrams, Table fo Field Variables, and Graph Choice Chart.
Hypothesis or Claim—
a well reasoned possible answer to a research question, an assertion, based on how the researcher thinks a particular system works, or a model of how a system works
the data and information collected in the course of the research project
the drawing of inferences or conclusions about the claim, based on the evidence
something (also called a factor or attribute) that can change or be altered, and measured
- Research Question and Hypothesis Brainstorming Worksheet
- Hypothesis Statement worksheet
- Table of Field Variables
- Understand that a hypothesis is a well reasoned possible answer to a research question, an assertion, based on how the researcher thinks a particular system works, or a model of how a system works
- Be able to relate the system model (drawing or other model) to their specific study site
As hypothesis development is an iterative process it may take some time. You may want to limit this activity to two class periods: one for general classroom discussion and one for group discussion.
Doing the Activity
Divide students into working groups (this can be done as a whole class also). Make sure each group has background material and the diagrams that they produced in earlier Units. Diagrams are the students’ models of the system that they are studying, and therefore the starting point for their thinking about how they think the system works.
Take a look at the "Teacher's Guide," it may aid you in helping the students brainstorm.
Have the students review their diagrams, and any notes they have made; thinking through all of the elements of the system and making sure that they can answer overarching system questions before asking them to brainstorm questions
You will almost certainly want to spend some time with each group going over their questions, making sure that the students have a workable model and a model that they understand. Once you are comfortable that a group has a model of what they think is happening, you can start guiding them toward some testable hypotheses.
Have students write down as many questions as possible (Brainstorm sheet), then work through the hypothesis worksheet (Hypothesis Statement worksheet) for each to determine how they would answer the questions. They will have to turn each question into a hypothesis to do this. This step (all of the steps) has the effect of weeding out non-testable questions.
Listen in on the brainstorming and reasoning within the groups.
Informally have student groups briefly present their questions to the rest of the class. Make sure that they explain the thinking behind the question. Students will also need to explain what data they will need to help them answer this question. Have students write a research proposal complete with question, hypothesis, sampling scheme and hypothetical graphs.
Lesson Extensions and Supplements
- Table of Field Variables
- Brainstorming Worksheet
- Hypothesis Statement Worksheet
- Teacher Guide