Using a Methodical Approach: The Scientific Method
Scientists seek to answer questions using a sequence of steps commonly called the scientific method. The scientific method is simply a procedure for organizing observations, making educated guesses, and collecting new information. The scientific method can be summarized as the following steps:
1 Ask a question. Scientists begin by asking, “Why does that happen?” or “How does that work?” Any question can be the start of your scientific journey. For example, “Why are my socks, which used to be white, now colored pink?”
2 Form a hypothesis that answers your question. A hypothesis is a proposed answer to your question: an educated guess based on what you already know. In science, a hypothesis must be testable, meaning that you (or someone else) must be able to determine if the hypothesis is true or false through an experiment. For example, “I think my socks turned pink because I washed them with pink laundry soap.”
3 State a prediction based on your hypothesis that can be tested. Using the proposed explanation in your hypothesis, form a prediction that you can test. For example, “I predict that if I wash a white T-shirt with pink laundry soap, it will turn from white to pink.”
4 Design an experiment to test your prediction. A good experiment is designed to best answer your question (see the upcoming “Testing your hypothesis: Experiments” section) by controlling as many factors as possible. For example, to test the above prediction, I will wash one white T-shirt with white laundry soap and one white T-shirt with pink laundry soap. I will wash them in the same washing machine with the same type of water so that everything (except the soap) is the same.
5 Perform the experiment. Time to do the laundry! If my prediction is correct, the shirt washed with pink soap will turn pink.
6 Observe the outcome. Both white T-shirts are still white after being washed with the different types of soap.
7 Interpret and draw conclusions from the outcome of the experiment. Scientists may run a single experiment multiple times in order to get as much information as possible and make sure that they haven’t made any mistakes that could affect the outcome. After they have all this new information, they draw a conclusion. For example, in my experiment, it appears that the color of the laundry soap is not what turns white T-shirts pink in the washing machine. At this point I can propose a new hypothesis about why my T-shirts have turned pink, and I can conduct a new experiment.
8 Share the findings with other scientists. This is possibly the most important step in the process of science. Sharing your results with other scientists provides you with new insights to your questions and conclusions. In my example, I did not confirm my hypothesis. Quite the opposite: I confirmed that the color of the laundry soap is not responsible for changing the color of my T-shirts. This is still very important information for the community of scientists trying to determine what, exactly, turns white T-shirts pink in the washing machine. Knowing my results will lead other scientists to develop and test new hypotheses and predictions.
Next, I describe in more detail each step of the scientific method approach to answering questions.
Sensing something new
The first step in the scientific method is simply to use your senses. What do you see, feel, taste, smell, or hear? Each of your senses helps you collect information or observations of the world around you. Scientific observations are information collected about the physical world without manipulating it. (Manipulations come later, with experiments; keep reading for the details!)
After you have collected multiple observations, you may find that there is a pattern — each dog you pet feels soft — or you may find that some observations are different from the others — most of the dogs have brown fur, but some have white fur with black spots. By summarizing your observations in this way, you prepare to take the next step in the scientific method, developing a hypothesis.
I have a hypothesis!
After you have summarized your observations, it’s time to propose an educated guess about the processes behind the patterns you observe. That educated guess is your hypothesis. In everyday speech people often say, “I have a theory” when they really mean “I have a hypothesis.” (I’ll get to theories in a few pages.)
Testing your hypothesis: Experiments
Now the real fun begins: experimenting to determine if one of your hypotheses is correct. Scientists use their hypotheses to develop predictions that can be tested. Based on the observations about the color of dog fur, a prediction could be this: “I predict that all dogs have either brown fur or white fur with black spots.” The prediction is a restatement of my hypothesis, based on my observations.
To determine if my prediction is correct I need to collect more information. I will make new observations, but this time I will manipulate the situation and observe the outcome. In other words, this time my observations will be the result of an experiment.
In most cases it’s impossible to observe every single instance of the physical world that you are exploring. Therefore, you must take a sample that can represent the rest. For example, I can’t look at every dog in the world to see what color their fur is, so I may decide that looking at 100 dogs will provide me with enough observations to determine if my prediction is correct. Those 100 are a sample of the worldwide population of dogs. If I choose those 100 dogs wisely, they may be a very accurate representation of the worldwide dog population. The best sample size is different for each experiment; it all depends on the question being asked.
