Student Handout 3.2.1
Developing A Testable Hypothesis
Scientific methods and experimentation depend upon scientific observations. After making observations, the
scientist thinks about what could be happening to cause the observation or what the effect would be of another
factor on the observations.
Predictions are important in science since they help us think about how one environmental factor may
affect another. An example of a prediction is, “Using my Interactive Notebook will increase my science grade.”
Predictions, however, do not go far enough. The next step is formalizing the prediction into a hypothesis, a
tentative and testable statement about the relationship between two variables.
A hypothesis is based on observations, provides an explanation about the relationship of the variables, and
clearly identifies a testable experiment within the statement. A student must be able to design an experiment
that supports (or rejects) the hypothesis. The experiment will determine if one variable really does affect some
other factor. In the case above, a possible hypothesis might be, “If I use my Interactive Notebook daily, then
my science grade might improve because I learned the material in small chunks which is better for absorbing
complex material like science.” This is an example of a common form for a hypothesis: If…(action of independent
variable), then…(action of dependent variable), because…(explanation).”
When developing a good hypothesis, you should be able to answer, “Yes” to the following four questions:
1. Is there a condition that sets up an effect? In other words, what do you think is the relationship
between the independent and dependent variables?
This is a simple statement that explains what you think the relationship is. Many times it can be written
in an “if…then…because…” format: If this condition occurs, then this effect is produced because this is
happening. Having just the condition and effect is not enough. The variables have to be measureable.
Teacher Note: Students often confuse use of the words “then” and “than.” Remember that the word THAN is
a comparative while THEN signifies an order in time.
2. Does the hypothesis lead to an experiment?
The hypothesis must be something that can be tested. For example, a hypothesis such as, “An increase in
asthma is due to the increase in atmospheric carbon dioxide,” is not testable. However, “Plants subjected
to classical music while growing will grow taller than plants that are subjected to silence,” is a testable
hypothesis.
3. Is it clear and objective?
A hypothesis must be easy to understand. The sentence structure should be mechanically correct and as
short as possible, saying only what is necessary. A hypothesis is a formal statement that does not use the
word “I.” It is free of personal bias and is based on background information and research.
4. Does it explain the reason for the prediction?
Hypotheses explain predictions using previous observations, research, or other background knowledge.
A hypothesis is not a guess, but is an educated statement that gives an explanation for an occurrence.
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xample: If “bubble wrap” is wrapped around exposed water pipes in the winter then
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the pipes will be less likely to freeze than if they were wrapped in newspaper because
heat does not transfer as readily through the air in the bubble wrap.
The Write Path I Science Teacher Guide