Name: science inquiry: testing ideas with evidence
Uploaded: 2026-06-01T06:28:24.252Z
Duration: 1 min 32 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Life Sciences

from-molecules-to-organisms-structures-and-processes

From Molecules To Organisms: Structures And Processes

HS-LS1-2

The Scientific Method

The scientific method is a detailed, stepwise process for answering questions.It begins with observations. For example, a scientist observes that slugs destroy some cabbages, but not those growing near garlic.These observations raise a question: could garlic be used to keep slugs from damaging a cabbage patch?To answer this question, the scientist develops a hypothesis, which is a possible explanation for the observation that leads to a testable prediction.In this case, the hypothesis is that garlic repels slugs. This predicts that cabbages surrounded by garlic powder will suffer less damage than those without it.The scientist tests this hypothesis by running an experiment designed to rule out other explanations.The scientist defines variables. An independent variable is the factor being tested, in this case, the addition of garlic. The dependent variable is the measurement used to track the outcome, such as the number of slugs on the cabbages.The cabbage plants are divided into control and experimental groups. The control group grows without garlic, while the experimental group grows with garlic powder.After the experiment, the data are collected and analyzed. If the control group shows a higher number of slugs on the cabbages than the experimental group, the result supports the hypothesis. A similar number of slugs in both groups indicates the hypothesis is not supported.The findings are then shared through publication so other scientists can review and repeat the experiment. Consistent results validate the work and form scientific theories.

the scientific method

The scientific method is a detailed, empirical problem-solving process used by biologists and other scientists. This iterative approach involves formulating a question based on observation, developing a testable potential explanation for the observation (called a hypothesis), making and testing predictions based on the hypothesis, and using the findings to create new hypotheses and predictions.Generally, predictions are tested using carefully-designed experiments. Based on the outcome of these experiments, the original hypothesis may need to be refined, and new hypotheses and questions can be generated. Importantly, this illustrates that the scientific method is not a stepwise recipe. Instead, it is a continuous refinement and testing of ideas based on new observations, which is the crux of scientific inquiry.Science is mutable and continuously changes as scientists learn more about the world, physical phenomena and how organisms interact with their environment. For this reason, scientists avoid claiming to &#x2018;prove&#x27; a specific idea. Instead, they gather evidence that either supports or refutes a given hypothesis.<h4>Making Observations and Formulating Hypotheses</h4>A hypothesis is preceded by an initial observation, during which information is gathered by the senses (e.g., vision, hearing) or using scientific tools and instruments. This observation leads to a question that prompts the formation of an initial hypothesis, a (testable) possible answer to the question. For example, the observation that slugs eat some cabbage plants but not cabbage plants located near garlic may prompt the question: why do slugs selectively not eat cabbage plants near garlic? One possible hypothesis, or answer to this question, is that slugs have an aversion to garlic. Based on this hypothesis, one might predict that slugs will not eat cabbage plants surrounded by a ring of garlic powder.A hypothesis should be falsifiable, meaning that there are ways to disprove it if it is untrue. In other words, a hypothesis should be testable. Scientists often articulate and explicitly test for the opposite of the hypothesis, which is called the null hypothesis. In this case, the null hypothesis is that slugs do not have an aversion to garlic. The null hypothesis would be supported if, contrary to the prediction, slugs eat cabbage plants that are surrounded by garlic powder.<h4>Testing a Hypothesis</h4>When possible, scientists test hypotheses using controlled experiments that include independent and dependent variables, as well as control and experimental groups.An independent variable is an item expected to have an effect (e.g., the garlic powder used in the slug and cabbage experiment or treatment given in a clinical trial). Dependent variables are the measurements used to determine the outcome of an experiment. In the experiment with slugs, cabbages, and garlic, the number of slugs eating cabbages is the dependent variable. This number is expected to depend on the presence or absence of garlic powder rings around the cabbage plants.Experiments require experimental and control groups. An experimental group is treated with or exposed to the independent variable (i.e., the manipulation or treatment). For example, in the garlic aversion experiment with slugs, the experimental group is a group of cabbage plants surrounded by a garlic powder ring. A control group is subject to the same conditions as the experimental group, with the exception of the independent variable. Control groups in this experiment might include a group of cabbage plants in the same area that is surrounded by a non-garlic powder ring (to control for powder aversion) and a group that is not surrounded by any particular substance (to control for cabbage aversion). It is essential to include a control group because, without one, it is unclear whether the outcome is the result of the treatment or manipulation.<h4>Refining a Hypothesis</h4>If the results of an experiment support the hypothesis, further experiments may be designed and carried out to provide support for the hypothesis. The hypothesis may also be refined and made more specific. For example, additional experiments could determine whether slugs also have an aversion to other plants of the Allium genus, like onions.If the results do not support the hypothesis, then the original hypothesis may be modified based on the new observations. It is important to rule out potential problems with the experimental design before modifying the hypothesis. For example, if slugs demonstrate an aversion to both garlic and non-garlic powder, the experiment can be carried out again using fresh garlic instead of powdered garlic. If the slugs still exhibit no aversion to garlic, then the original hypothesis can be modified.<h4>Communication</h4>The results of the experiments should be communicated to other scientists and the public, regardless of whether the data support the original hypothesis. This information can guide the development of new hypotheses and experimental questions.

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Education

JoVE Core

Biology

Fundamentals

Scientific Inquiry

KEY TERMS AND CONCEPTS

science inquiry: testing ideas with evidence

Science inquiry uses evidence to test ideas and refine them over time. Biologists and other scientists begin with observations made by the senses or by scientific tools. Those observations lead to a question and then to a hypothesis, which is a testable possible explanation.

A good hypothesis must be falsifiable, which means it can be disproven if it is wrong. Scientists also think about the null hypothesis, which is the opposite idea being tested. In the slug and cabbage example, one hypothesis is that slugs avoid garlic. The prediction is that slugs will not eat cabbage plants surrounded by garlic powder.

Scientists often test hypotheses with controlled experiments. These experiments include an independent variable, which is the factor expected to have an effect, and a dependent variable, which is the measurement used to see the result. In the slug experiment, garlic powder is the independent variable, and the number of slugs eating the cabbages is the dependent variable. Experiments also need an experimental group and a control group.

The experimental group is exposed to the independent variable. The control group is kept under the same conditions, except for that variable. In the slug example, control groups might include cabbage plants surrounded by a non-garlic powder ring to control for powder aversion and cabbage plants with no ring at all to control for cabbage aversion. Without a control group, it is hard to know whether the result came from the treatment or from something else.

The scientific method is not a fixed recipe. It is a cycle of testing, checking, and improving ideas based on new observations. If results support a hypothesis, scientists may run more experiments and make the hypothesis more specific. For example, they could test whether slugs also avoid other Allium plants, such as onions.

If the results do not support the hypothesis, scientists first rule out problems with the experiment. If slugs avoid both garlic and non-garlic powder, the test could be repeated with fresh garlic instead of powdered garlic. If slugs still show no aversion to garlic, the original hypothesis may need to change. Scientists do not usually claim to prove an idea. They gather evidence that supports or refutes it.

The final step is communication. Scientists share their results with other scientists and the public, whether or not the data support the original hypothesis. That information helps create new questions, new hypotheses, and new experiments.

Science Inquiry: Testing Ideas with Evidence

science-inquiry-testing-ideas-with-evidence

Science inquiry uses evidence to test ideas and refine them over time. Biologists and other scientists begin with observations made by the senses or by scientific tools. Those observations lead to a question and then to a hypothesis, which is a testable possible explanation. A good hypothesis must be falsifiable, which means it can be disproven if it is wrong. Scientists also think about the null hypothesis, which is the opposite idea being tested. In the slug and cabbage example, one...

inductive reasoning

Inductive Reasoning in Biology

Inductive reasoning in biology uses observations to build a general conclusion. It starts with related evidence and moves toward an idea that seems credible. Because the conclusion is not certain, inductive arguments can be strong or weak rather than valid or invalid. This kind of reasoning is common in descriptive science. A life scientist makes observations and records them. The data can be qualitative or quantitative. Scientists can also add drawings, pictures, photos, or videos to support...

deductive reasoning

Deductive Reasoning in Science Experiments

Deductive reasoning helps scientists turn a general idea into a specific test. It is the kind of logic used in hypothesis-based science, where researchers start with a rule or principle and predict what should happen next. This is the opposite direction from inductive reasoning, which begins with observations. With deductive reasoning, a scientist can make an if-then prediction from a hypothesis. For example, a researcher may hypothesize that butterflies are attracted to certain flowers...

correlation and causation

Testing Relationships in Biology Data

Statistical tests can show whether two variables are related. This relationship is called a correlation. The variables may be independent and dependent, and the data may show a positive or negative pattern. If no consistent relationship appears, then there is no correlation. A positive correlation means the dependent variable increases as the independent variable increases. A negative correlation means the dependent variable decreases as the independent variable increases. Correlation shows...

key terms and concepts

Learn how observations lead to testable hypotheses, controlled experiments, and evidence-based conclusions using a simple slug and cabbage example.

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Ohio’s Learning Standards and Model Curriculum

9-12

Human Anatomy and Physiology

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BIO.1

BIO.1.a

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CH.1

CH.1.a

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ES.1

ES.1.a

ES.1.b

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LS.1.a

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SC.912.N.2.1

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PHYS.1

PHYS.1.A

PHYS.1.B

PHYS.3

PHYS.3.A

PHYS.3.C

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IPC.1

IPC.1.A

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HS-LS1-1

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HS-LS1-3

Science Inquiry: Testing Ideas with Evidence

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