[Sophomore Biology at GHS: The Scientific Method]

The Scientific Method


Science is an organized way of using evidence to learn about the natural world.

The goal of science is to investigate and understand the natural world, to explain events in thenatural world, and to use those explanations to make useful predictions.

The Scientific Method Itself:

I. Observations:

Whether they start with a problem or not, scientists make careful observations.

Observations are a way to collect data (recorded observations or information) about events or processes in a careful, orderly way, using the senses (sight, hearing, touch, taste and smell).

Two types of data include:

a) Quantitative data: Are observations which collect data that can be directly measured or counted.

b) Qualitative data: Are observations involve making careful descriptions or drawings and do not involve numbers.

Inference: A logical interpretation of an observation based on prior knowlege. An educated guess as to what is occurring.

II. Hypothesis:

A proposed scientific explanation for a set of observations. Scientists devise hypotheses based on logical inferences, prior knowledge and informed, creative imagination.

Hypotheses may be tested by controlled experiments, or by collecting additional data.

III. Controlled Experiment:

A way to test a hypothesis by testing a single variable by changing it while keeping all other variables the same.

Variable: Any factor during an experiment that could change and affect the results (Examples: Temperature, pressure, amount of light, color of light, human error, etc......)

Manipulated variable: The factor in an experiment that is deliberately changed to test the hypothesis.

Controlled variable: any factor during an experiment that a scientist purposely keeps the same.

During the experiment, a scientist divides the tests into 2 groups, the control setup and the experimental setup.

Experimental setup: The part of the experiment that contains the manipulated variable.

Control setup: The part of the experiment that does not contain the manipulated variable. It may be called the placebo.

[Example #1] [Example #2]

Dependent Variable / Measured Variable: The variable we are measuring to determine whether a change has occurred. In the diagram above, the mass is the dependent variable, because the mass of the plants is dependent upon the independent variable, time.

Independent Variable: A variable that does not depend upon another. It acts independently of other variables. (Examples: Time, Dates)

[Example #1] [Example #2]

IV. Conclusion:

Theory: A well-tested explanation that unites a wide range of observations.