2.2 The Scientific Method

Many scientists study the living world by posing questions and seeking evidence-based responses. This approach is referred to as the scientific method. The scientific method was used even in ancient times, but it was first documented by England’s Sir Francis Bacon (1561– 1626), who used observation and inductive methods for scientific inquiry. The scientific method can be applied to almost all fields of study as a logical, rational problem-solving method. As Zora Neale Hurston said, “Research is formalized curiosity. It is poking and prying with a purpose.” The scientific method is a format for formalized curiosity.

Proposing a Hypothesis

A hypothesis suggests a testable explanation for an event. Think of it like this: If answering a research question is the goal of a study, then a hypothesis is an educated guess at the answer.

Suppose one Monday morning, a student arrives at class and quickly discovers that the classroom is too warm. That is an observation that also describes a problem: the classroom is too warm. The student then asks a question: “Why is the classroom so warm?”

One hypothesis might be, “The classroom is warm because no one turned on the air conditioning.” But there could be other responses to the question, and therefore other hypotheses may be proposed. A second hypothesis might be, “The classroom is warm because there is a power failure, and so the air conditioning doesn’t work.”

Once a hypothesis has been selected, the student can make a prediction. A prediction is similar to a hypothesis but it typically has the format “If . . . then . . . .” For example, the prediction for the first hypothesis might be, “If the student turns on the air conditioning, then the classroom will no longer be too warm.” Looking for “if … then …” statements in scientific writing is one way to easily identify the study’s hypothesis(es).

Testing a Hypothesis

A valid hypothesis must be testable. It should also be falsifiable, meaning that it can be disproven by experimental results. Importantly, science does not claim to “prove” anything because scientific understandings are always subject to modification with further information. This step – openness to disproving ideas – is what distinguishes sciences from non-sciences or pseudoscience. The presence of the supernatural, for instance, is neither testable nor falsifiable.

To test a hypothesis, a researcher will conduct one or more experiments designed to eliminate one or more of the hypotheses. Each experiment will have one or more variables and one or more controls. A variable is any part of the experiment that can vary or change during the experiment. The control group contains every feature of the experimental group except it is not given the manipulation that is hypothesized about. Unfortunately, it is not possible to control for every variable. In these cases, scientists report and account for confounding variables.

When testing a hypothesis or analyzing data, there are two primary variables used. An independent variable is one that the researcher does not control regardless of the question asked or test conditions, though they can choose which independent variables to collect. For example, your height does not change simply because you move to a different room. Height is an independent variable. However, a scientist might not ask about your height if their research is about weight and exercise. A dependent variable changes according to the independent variable or through direct influence from the researcher. It is a thought, action, or measurement that may change based upon interventions from the study (experiment) or individual characteristics (age group). For example, whether you like dogs (dependent variable) may change based upon whether you had pets as a child (independent variable).

Returning to the student in the warm classroom, to test the first hypothesis, the student would find out if the air conditioning is on. If the air conditioning is turned on but does not work, there should be another reason, and this hypothesis should be rejected. To test the second hypothesis, the student could check if the lights in the classroom are functional. If so, there is no power failure and this hypothesis should be rejected. Each hypothesis should be tested by carrying out appropriate experiments. Be aware that rejecting one hypothesis does not determine whether the other hypotheses can be accepted; it simply eliminates one hypothesis that is not valid. Using the scientific method, the hypotheses that are inconsistent with experimental data are rejected.

While this “warm classroom” example is based on observational results, other hypotheses and experiments might have clearer controls. For instance, a student might attend class on Monday and realize she had difficulty concentrating on the lecture. One observation to explain this occurrence might be, “When I eat breakfast before class, I am better able to pay attention.” The student could then design an experiment with a control to test this hypothesis.

In hypothesis-based science, specific results are usually predicted from a general premise using deductive reasoning. But the reverse of the process is also possible: sometimes, scientists reach a general conclusion from a number of specific observations via inductive reasoning. Inductive and deductive reasoning are often used in tandem to advance scientific knowledge.

Steps of the Process

The scientific method consists of a series of well-defined steps. If a hypothesis is not supported by experimental data, a new hypothesis can be proposed.

Figure 2 provides a detailed illustration of the scientific method. Note that these steps should be followed for each hypothesis, but you do not always need to run different experiments. Scientists often design studies in a way that can test more than one hypothesis with the same set of data. This might mean multiple experimental groups or the division of samples into more than one treatment or survey. Ultimately, we ask: Based on the results of the experiment, is the hypothesis correct? If it is incorrect, propose some alternative hypotheses and return to making predictions. These steps are:

• Observation – identify a problem or a question
• Question – identify variables
• Make a Hypothesis – educated guess at the answer
• Generate Aim/Prediction – what will happen if your hypothesis is correct
• Design a Controlled Experiment – keep in mind your independent, dependent, controlled, and confounding variables
• Observation and Collection of Data – the “research” part of research
• Analysis and Presentation of Data – often visual but may also be written
• Make Conclusions – does the data support or reject the hypothesis in question?

After these steps are complete, scientists can decide whether to repeat their study for replication and validity or create a new hypothesis and try again. This is also the point at which research is written up for publication – like those scholarly articles your professors always talk about.