Scientific Method Exercise

D. LaCole

INTRODUCTION

The scientific method is a series of ordered steps that scientists use to answer questions. Although the actual steps of the scientific method may vary, there are certain elements that all scientific inquiries should possess. In this exercise, we will review the required elements of the scientific method, and practice evaluating and conducting scientific investigations.

The steps of the scientific method:

1. Make careful observations

2. Recognize and state the problem

3. Develop a hypothesis

4. Make a prediction to be tested

5. Formulate and conduct experiment

6. Interpret results

1. Making careful observations is the necessary first step for all scientific inquiry. Initial observations provide the starting point for all scientific investigations because they generate questions. Usually the process begins when the investigator observes some phenomena that he or she finds interesting and desires to know more about. Sometimes, an investigator is already interested in a particular topic. Then, careful observations can help clarify which areas might be the most interesting to pursue.

2. Based on initial observations, the investigator must then recognize and state the problem he or she wishes to examine. This will usually be stated in the form of a question, for example, "Why is the grass green?", "What is the cause of AIDS?", "Why do plants bend towards a window?", etc. At this point, it is important to remember that NOT all questions can be answered scientifically. Only phenomena that are well defined, measurable, and controllable can be investigated with the scientific method.

3. Once the problem has been stated, the investigator formulates a hypothesis that attempts to provide a probable explanation for the observed phenomena. A hypothesis is an investigator's "best guess" as to why things are the way they are. For example, a hypothesis for the question "Why do plants bend toward a window?" could be; "Plants bend toward a window because they need light to grow". When formulating a hypothesis, there are three requirements that must be kept in mind:

1. the hypothesis must be reasonably consistent with well established facts

2. the hypothesis must be testable (remember, the scientific point of a hypothesis is not to be right, but to be testable...)

3. the hypothesis must be falsifiable (able to be proven false)

Finally, it is important to know that a hypothesis can never be proven true, especially with just one or a few experiments. Results from a scientific experiment can only support (or not support) a hypothesis. If a hypothesis is supported by a large number of experiments, it may then become a scientific theory, an idea that has wide acceptance in the scientific community.

4. In order to design an experiment, the investigator must formulate a prediction statement. The prediction statement is often in the form of an "if...then" statement, i.e., "If the hypothesis is correct, the results of the experiment will be...". An example of a prediction statement could be: "If plants need light to grow, then plants placed in darkness will not grow..." The prediction states what will be tested in the experiment.

5. The investigator must next design an experiment that will directly test the prediction statement. An important part of designing an experiment is identifying the variables, of which there are three categories:

1. A dependent variable is what the investigator measures, counts, or records. It is what the investigator thinks will be affected during the experiment. There may be one or several dependent variables in any one experiment.

2. An independent variable is what the investigator thinks will affect the dependent variable(s). There can be only one independent variable for any one experiment.

3. A controlled variable is any variable that is held constant during the experiment. These variables must be held constant so that the investigator can be sure any observed effects on the dependent variable(s) are due only to the independent variable.

6. Once the experiment has been conducted, the final step involves interpreting the results. It is in this step that the investigator determines whether or not the data supports the original hypothesis. If the data supports the hypothesis, then the investigator may suggest further experimentation that could contribute to the support of that hypothesis. If the hypothesis is not supported by the data, the experiment still has value. The investigator may wish to repeat the experiment, reformulate the hypothesis or design a new experiment.

PART I - SAMPLE HYPOTHESES

Determine whether or not each of the following hypotheses can be tested using the scientific method. Remember, for a hypothesis to be considered "good" it must be consistent with well-established facts, testable, and falsifiable.

1. Most of the energy coming from the Sun is in the form of visible light.

2. Unicorns live in the woods of Georgia.

3. Shelley wrote beautiful poetry.

4. Diamond is harder than steel.

5. Diamond is more beautiful than ruby.

6. Detergent A cleans clothes better than detergent B.

7. Coke tastes better than Pepsi.

8. Invisible fairies turn the grass green every spring.

9. Birds are neat.

10. Bird-watching is one of the most popular leisure activities among Americans.

PART II - VARIABLES

Identify the dependent and independent variables in each of the following experiments.

1. Batches of seeds are soaked in salt solutions of different concentrations. Germination is counted for each batch.

2. Guinea pigs are kept at different temperatures for 6 weeks. At the end of that time, percent weight gain is recorded.

3. Percent absorption by a pigment is measured for red, blue, green, and yellow wavelengths of light.

4. The height of bean plants is recorded daily for a period of two weeks.

REFERENCES

Morgan, J. G. and E. B. Carter. Investigating Biology. Redwood City, CA: The Benjamin/Cummings Publishing Company, Inc., 1993.

Solomon, E. P. and L. R. Berg. The World of Biology. Philadelphia: Saunders College Publishing, 1995.