Biology 198
Fall semester sections 07500 and 07510; Ackert 219; WF 1:30-3:20 pm

Updated: 24 August 2000

Introduction to the Scientific Method

Components of the Scientific Method
(*most universally accepted as a step in the scientific method)

  1. *Observation: A good scientist is observant. He/she becomes curious and raises a question about it.
  2. *Hypothesis (hypo = under/beneath; thesis = to arrange): This is a "tentative" answer to the question; an educated explanation for what was observed. It is not a real explanation; only a tentative one. Hypotheses reflect past experience with similar questions and should be testable using experimentation and deductive reasoning. Hypotheses can be proven incorrect, but cannot be "proven" with absolute certainty. In the future, more knowledge may reveal a case where the hypothesis is not true. A hypothesis may be of two different forms:
    1. Proximate hypothesis (proximate cause) - What exactly causes the observable changes? Proximate causes are often testable using the scientific method and are often defined as "how" questions.
    2. Ultimate hypothesis (ultimate cause) - What are the "reasons" behind the mechanisms? Ultimate causes may or may not be testable using the scientific method. These often involve behavior of an organism, and many ultimate causes are philosophical in nature and may not be testable with our current state of knowledge. Ultimate causes are often defined as "why" questions.
  3. Prediction: Some individuals include the "prediction" as a component of the scientific method whereas other individuals do not. This is not a component of the scientific theory in this class. Here, the experimenter may use the hypothesis to make a specific or general prediction using one of two types of reasoning:
    1. Inductive reasoning goes from specific observations to general conclusions. For instance, you observe bacteria in the intestines of 5 different species of vertebrates (specific observations) and then predict that ALL vertebrates have intestinal bacteria (a general conclusion).
    2. Deductive reasoning goes in the opposite direction; from generalizations to specifics. For instance, if all vertebrates have intestinal bacteria, and cattle are vertebrates, then cattle must have intestinal bacteria. Often we make hypotheses without going so far as to make a prediction.
  4. *Experiment (testing): The scientist performs the experiment, usually series of experiments, to see if the predicted results are obtained. If the expected results are obtained, that lends support to the hypothesis. Each experiment must be "controlled;" i.e. the scientist must contrast an "experimental group" with a "control group." The two groups are treated EXACTLY alike except for the ONE variable being tested. The concept of using the appropriate control groups in an experiment is extremely important, and is THE most important fundamental concept to be learned by a graduate student.
  5. Repetition. This is oftentimes included within the definition of the experiment itself. Every experiment should be repeated several times and, if possible, also in various ways. Random chance and unpredicted outside influences may affect the data, especially if only a single experiment is performed. Repetition helps eliminate errors and allows consistency. Statistics is a highly useful tool in helping scientists keep a handle on variability.
  6. Conclusions and modifications of the hypothesis. Oftentimes courses include the conclusions and modifications as a component of the experiment itself and, thus, they are usually not mentioned. Once the experiment is over, one analyzes the data and determines if the information supports the hypothesis. Often, the hypothesis will need to be modified or changed after the experiment.
  7. *Formulate a theory: When enough experiments have been performed and consistency is obtained, the hypothesis may become a theory and provides a coherent set of propositions which explain a class of phenomena. Sometimes it takes many years and hundreds of experiments before a theory is formulated; thus, many classes do not include the theory as a component of the scientific method. A theory is then a framework within which observations are explained and predictions are made. It is NOT a guess nor a hunch; it is a concept built logically through testable observations and hypotheses.
  8. NOTE: Scientists perform controlled experiments and publish the results of these experiments in peer reviewed (refereed) journals. This is the basis for all scientific knowledge; observable, measurable, and repeatable phenomena. A "belief" is something that one takes on faith, is accepted without empirical evidence, and falls into the realms of philosophy and religion. Thus, a belief is NOT something that has been demonstrated using the scientific method. Scientists NEVER rely on testimonials (anecdotes), and researchers openly publish all details of their scientific methods for others to evaluate. Because science is not a collection of unassailable truths, other scientists are always encouraged to retest and refine the methods and conclusions. Truth will remain the truth despite the intensity of scrutiny. Scientific research is cumulative and progressive; scientists build on the work of previous researchers.

Hypothesis versus Theory

  1. A hypothesis is a working assumption. A testable, tentative explanation. Typically, a scientist devises a hypothesis and then tests it against available data (obtained from previous experiments and observations) to see if it holds up under close scrutiny. If the hypothesis holds up under experimentation, the scientist may declare it to be a theory.
  2. A theory is a conceptual framework or general set of principles, larger in scale than a hypothesis and supported by scientific evidence, that explains existing observations and predicts new ones. "A good theory must satisfy two requirements: It must accurately describe a large class of observations on the basis of a model that contains only a few arbitrary elements, and it must make definite predictions about the results of future observations." Steven Hawkins.

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