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1.3: Developing Hypotheses

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    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 CO2 has been increasing since 1958. This leads us to ask the following: why is atmospheric CO2 increasing?

    Possible Answers to the Question

    A hypothesis is a reasonable explanation for a small range of phenomena. A hypothesis is limited in scope; it attempts to explain a single event or a fact. A hypothesis must be testable and falsifiable. In other words, we must be able to test it, and we must be able to disprove it.

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

    • CO2 is released into the atmosphere by volcanoes when they erupt.
    • CO2 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 CO2 has increased over the past five decades because the amount of CO2 gas released by volcanoes has increased.

    Hypothesis 2

    The increase in atmospheric CO2 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 existing scientific literature to see if either of these hypotheses can be disproved, or if one or both can be supported by the data.


    • A hypothesis is a reasonable explanation for a small range of phenomena.
    • A scientific hypothesis must be both testable and falsifiable.
    • If two or more hypotheses are being tested, they are called multiple working hypotheses.


    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 concept?

    Explore More

    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 scientific hypothesis?
    4. Write an example of a hypothesis, and explain how you would test it.

    This page titled 1.3: Developing Hypotheses is shared under a CK-12 license and was authored, remixed, and/or curated by CK-12 Foundation via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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