nhName:_______________________________
Writing Hypotheses
To learn about what is not known or to verify a notion, the scientific method might be
carried out and an actual experiment may be conducted. It does not matter if your
experiment has been done a thousand times before or that your teacher may already know
the results. What matters is that you don’t know the results and that you can
independently find a verifiable answer. In a formal experiment, a formal hypothesis
should be written before an experiment is performed.
What is a Formal Hypothesis?
A hypothesis is a tentative statement that proposes a possible explanation for some
phenomenon or event. A useful hypothesis is a testable statement, which may include a
prediction. A hypothesis should not be confused with a theory. Theories are general
explanations based upon a large amount of data. For example, the theory of evolution
applies to all living things and is based on a wide range of observations. However, there
are many things about evolution that are not fully understood.
When are Hypotheses Used?
The key word is testable. That is, you will perform a test of how two variables might be
related. This is imperative when you conduct an experiment. You test variables.
Usually, a hypothesis is based on some previous observation such as noticing that in
November many trees undergo color changes in their leaves while the average daily
temperatures are dropping. Are these two events connected? How?
Any laboratory procedure that you follow without a hypothesis is not really an
experiment. It is just an exercise or demonstration of what is already known.
How are Hypotheses Written?
1. Salt in soil may affect plant growth.
2. Plant growth may be affected by the color of the light.
3. Bacterial growth may be affected by temperature.
4. Ultraviolet light may cause skin cancer.
5. Temperature may cause leaves to change color.
All of these are examples of questions that can be used to develop a hypothesis.
Practice:
Choose three of the above questions and do the following: 1) Identify the Independent
Variable (IV), and Dependant Variable (DV), 2) Write a formal hypothesis with the
correct “If variable is related to variable then prediction.”
1. IV:
DV:
Hypothesis:
2. IV:
DV:
Hypothesis:
3. IV:
DV:
Hypothesis:
Now create two questions that you might investigate on your own. Then do what you did
above.
4. Question:
IV:
DV:
Hypothesis:
5. Question:
IV:
DV:
Hypothesis: