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Development of Hypotheses

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Development of Hypotheses

What is a hypothesis?

An educated guess? Is that what you learned a hypothesis is? Lots of people have learned that, but it’s not exactly right. So what is a hypothesis? There are two hypotheses listed below. They address a question about carbon dioxide in the atmosphere. Check out what those hypotheses are. Then we'll see what to do with them next.

Asking a New Question

First, we need to find a question that we want to answer. Let's start with the fact that atmospheric CO 2 has been increasing since 1958. This leads us to ask the following: why is atmospheric CO 2 increasing?

Possible Answers for the Question

A hypothesis is a reasonable explanation to explain a small range of phenomena. A hypothesis is limited in scope; it explains a single event or a fact. A hypothesis must be testable and falsifiable . We must be able to test it. And we must be able to disprove it.

Back to answering the question. We do some background research to learn the possible sources of carbon dioxide into the atmosphere. We discover that there are at least two (there are actually many more):

  • CO 2 is released into the atmosphere by volcanoes when they erupt.
  • CO 2 is released when fossil fuels are burned.

From these two facts, we can create two hypotheses; we will have multiple working hypotheses . We can test each of these hypotheses. We can prove either or both of these hypotheses false. In this case, it's even possible that both are true.

Hypothesis 1

Atmospheric CO 2 has increased over the past five decades because the amount of CO 2 gas released by volcanoes has increased.

Hypothesis 2

The increase in atmospheric CO 2 is due to the increase in the amount of fossil fuels that are being burned.

Usually, testing a hypothesis requires making observations or performing experiments. In this case, we will look into the scientific literature to see if either of these hypotheses can be disproved. Or if one or both can be supported by the data.


  • falsifiable : Able to be proven false by an observation or experiment.
  • hypothesis : Good working explanation for a problem; a hypothesis can be tested.
  • multiple working hypotheses : Two or more hypotheses that can be tested simultaneously or in sequence.
  • testable : Able to be evaluated critically, usually using data.


  • A hypothesis is a reasonable explanation of a phenomenon.
  • A scientific hypothesis must be testable. A scientific hypothesis must be falsifiable.
  • If two or more hypotheses are being tested it is called multiple working hypotheses.


Use the resource below to answer the questions that follow.

  1. What is a hypothesis?
  2. Why is it important to have a specific hypothesis?
  3. How can you test a hypothesis?
  4. Write an example of a hypothesis, and explain how you would test it?


  1. How is a hypothesis "a reasonable explanation”? Why is that a better definition than “an educated guess”?
  2. What if a hypothesis is shown to be wrong? Is the question the scientists are trying to answer a bad question?
  3. What are multiple working hypotheses? What are the two hypotheses proposed to answer the question in this lesson?

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