The Scientific Method

One of the most important things for new students to remember when they are trying to think like a scientist is to utilize the scientific method. This is a straightforward path of analysis that can help us solve tough problems or answer hard questions with a reliable and repeatable set-up. The scientific method helps scientists stay focused on their problem, gather various kinds of evidence, evaluate or analyze the evidence, and point to a possible solution. It also helps other scientists replicate or duplicate past studies to confirm or refute the analysis performed or the stated results.

The scientific method begins with observations and questions, which leads to research, hypotheses, and predictions. Once scientists have completed some observations and research, they often have specific questions (or hypotheses) they wish to test with experiments, models, or additional analysis (e.g., statistical). These tests or experiments are then completed, leading scientists to a final result or conclusion. Not all scientists will arrive at the same conclusion, even if they start from the same evidence and/or data, and the variety of conclusions can create some excellent discussions or debates.

Please explore the sections below on the importance and the use of the scientific method.

Learning Outcomes

After completing this online module, you should be able to:

  • List and describe the general steps of the scientific method,
  • Apply the scientific method critically in your academic work,
  • Use the scientific method to ask critical and logical questions, and
  • Design appropriate experiments.

The Scientific Method in a Nutshell

This video outlines and describes the inter-connections and flow of the Scientific Method within science, utilizing global climate change as our example, as it combines all the various science disciplines: Earth, Chemistry, Physics, and Biology. 



It can be challenging to understand all the Earth's processes and inter-workings because our planet is a dynamic body with many internal parts and a complex formation history. Throughout time, Earth has been experiencing continuous change, and this will continue into the foreseeable future. Occasionally, the changes are rapid and violent (e.g., earthquakes and volcanic eruptions); other times, they are small and slow (e.g., erosion and weathering). Scales of size, space, and time can vary greatly between the various phenomena found on our planet, further complicated by the addition of people and infrastructure.

A great deal of Earth Science and Geology is based on observing the Earth throughout time, and the changes and modifications it undergoes, and often requires expertise from many scientific and mathematic disciplines. It is the study of how the natural world works, how our environment affects us, and how we, in turn, affect the natural environment around us.

Earth and Environmental Science is part of the broader endeavor of SCIENCE, the systematic process for learning and testing our understanding of the world around us. The term SCIENCE also refers to the body of knowledge that arises from problem identification, observations, testing, and the discovery of new and exciting things. Earth and Environmental Science is an interdisciplinary field of study, incorporating concepts and techniques from other realms of science and technology.

Here is a quote from the late Carl Sagan: 

“We've arranged a global civilization in which the most crucial elements – transportation, communications, and all other industries; agriculture, medicine, education, entertainment, protecting the environment; and even the key democratic institution of voting – profoundly depend on science and technology.”

Sagan, C. (1997). The demon-haunted world: science as a candle in the dark. London: Headline.

Scientific ideas, methods, and knowledge evolve as new information and linkages are discovered, constantly pushing the discipline forward into new frontiers, and helping us avoid the mistakes of the past. Solutions to these new and old problems must be both global in scope, and sustainable over time, in order to be effective.

As we saw in the previous video, the scientific method involves several important and iterative steps:

Diagram showing the steps of the scientific method.



observations icon

All advances and studies in science begin with an observation of an interesting phenomenon or process that a scientist wishes to explain or understand more fully. Observations set the scientific method in motion and continue to be an important part of the entire procedure.

Young girl looking up at tree.


questions icon

All scientists are naturally curious about the world around them, how it works, and why we observe what we do. Why are certain plants or animals more or less common than at previous times in Earth’s history? Is climate change increasing storms and flooding? What causes the explosive outbreak of toxic algae in Lake Erie each summer? These are all examples of questions Earth and Environmental Scientists ask and attempt to answer during their research.

Three boys sitting in grassy area looking thoughtfully at something on the ground.


research icon

As scientists begin to look at a research or scientific problem, they start by identifying the issue, observing the complexity or inter-connections of the issue, and then researching and explaining how these individual processes work. This starts to build the knowledge base a scientist needs in order to attempt to answer or solve a complex real world problem. For example, in order to discover if climate change is increasing the intensity of storms and flooding, research on effects on precipitation factors would need to be undertaken first.

Three boys using a magnifying glass to examine a tree.



Before completing any experiment, scientists attempt to answer their own question(s) by devising explanations or statements which can be tested. A hypothesis is an educated guess to explain a phenomenon or what might happen in an experiment. For example, a fresh water scientist looking at algae growth in Lake Erie might state a hypothesis such as:

"Increased use of agriculture fertilizer in overland flow and runoff has increased the volume of nutrients reaching Lake Erie, causing an increase in the development and life cycle of toxic algae."

Two girls closely examining something in a jar.


Illustration of a brain with light bulbs surrounding it. Hypothesis is an educated guess.
There are four major concepts in science: facts, hypotheses, laws, and theories. In layman's terms, 'hypothesis' and 'theory' are often misused or incorrectly interchanged. However, in science, the two terms actually mean very different things. Above, we learned what was meant by a hypothesis (essentially an educated guess), whereas theories are supported by a vast body of empirical data and are already accepted by the majority of scientists within that area of scientific study (e.g., the theory of gravity, germ theory).
Illustration of a stack of books. Theory is based on vast body of empirical data.



Try to answer some of these simple multiple choice questions based on the reading above.

Select which of the following statement(s) are observations:

A hypothesis is ________.


predictions icon

Scientists use hypotheses and observations to make a prediction which they can then test for accuracy. These predictions are statements which can be directly tested. In the previous example of algae growth in Lake Erie, a scientist could predict:

"The addition of nutrients from increased fertilizer runoff will directly increase the amount of algae found in a fresh water body."

This is something which can be directly tested in a controlled experiment to gain more knowledge on the process in question.

Girl and her teacher making a prediction about something in a jar.

Test and Experiment

test and experiment icon

Observations, hypotheses, and predictions are all assessed during the experimental phase of the scientific method. An experiment is specifically designed to test a hypothesis or prediction by manipulating a set of variables, and quantifying some answer or result after completion. Depending on the results, the experiment may support (or not) the original observations and hypotheses. Experiments can be either:

  • a controlled or manipulative experiment (e.g. testing vegetation growth in a greenhouse), or
  • a natural uncontrolled experiment (e.g. testing vegetation growth in an open field).

It is always important for the scientist to accurately describe the experiment and how it is set up and run, so that other scientists can attempt to replicate the results for future studies. An experiment will return information in the form of one (or both) types of data: qualitative and quantitative. Qualitative data is often found in more social studies, but in general is data which cannot be easily expressed in numerical or statistical values (e.g., personal interviews, surveys, descriptive observations, etc.). Quantitative data is data which can be expressed with numerical or statistical values (e.g., temperature, speed, volume, mass, etc.).

Girl wearing safety glasses examining blue liquid in a test tube.

Results and Conclusions

results and conclusions icon

Once all experiments have been completed, the scientist can logically share their results and conclusions. This is often the form of a scientific research paper, published in an academic journal (e.g. Science, Nature, etc.) which takes the reader through the entire scientific method from start to finish. Experiments with results that support the hypotheses and observations can be explained and discussed, to show the inter-connections. However, experiments which fail to support a hypothesis are just as valid and useful, as it may force the scientist to rethink their understanding, change their hypothesis, and re-do the scientific method for a better result.

Fail to reject hypothesis. Test a new prediction

Reject hypothesis. Test a new hypothesis

Young child in a class excited over blue liquid bubbling out of a beaker.


An experiment ________.

You are interested in studying the impact of fertilizer runoff into the environment and decide to conduct a laboratory experiment by observing fertilizer application in a greenhouse. This is an example of a_________.


Take it with You

Here are some questions you can take with you to think about the applications of the scientific method:

  • What is the typical sequence of steps in the scientific method, using any real-world example? What is the difference between a manipulative experiment and a natural experiment? Can you provide examples of both?
  • What has to happen to a scientist’s research before it is publishable? Why is this process important?

Additional Resources

To enhance your understanding of the scientific method, please have a look at these resources:

  • The Teacher’s Pet: The scientific method (YouTube, 4:05)
  • Khan Academy: The scientific method (YouTube, 11:48)
  • Withgott, J.; Laposata, M.; Murck, B. (2017). Environment: the science behind the stories. (Third Canadian edition). (Chapters 1 and 2). New Jersey, USA: Pearson Education, Inc. 


This module has been developed by Dr. Keith Delaney in cooperation with the University of Waterloo Centre for Extended Learning, the Faculty of Science, and the Earth and Environmental Sciences department. 


Image Citations

  • Banner image courtesy of Man As Thep/iStock/Getty Images.
  • Picture frames courtesy of BoxerX/iStock/Getty Images.
  • Brain with bulbs courtesy of Polar_lights/iStock/Getty Images.
  • Stack of books courtesy of Sonya_illustration/iStock/Getty Images.