Scientific Method and Experimental Design

Steps in the Scientific Method 1. PROBLEM – Scientists make observations about nature and ask a question. 2. Make more observations or do some RESEARCH. 3. Formulate an explanation for the problem that can be tested – HYPOTHESIS (educated guess or a prediction – must be written “If ….then…….”.)

4. Design an EXPERIMENT. A controlled experiment is when a scientist collects data under controlled conditions. There are two groups; the control group and the experimental group.

The one factor that is altered between the two groups is called the INDEPENDENT VARIABLE (manipulating variable). The condition that results from the independent variable is called the DEPENDENT VARIABLE (responding variable - the one that you measure).

5. COLLECT DATA – using S.I. (metric system) data can be either qualitative (description eg. Darker or lighter) or quantitative (numbers/measurement eg. Height of trees)

6. ANALYZE and manipulate the data – Graph the data. 7. CONCLUDE: Was the hypothesis supported or not supported by the data? What other experiments might be done?

REPORTING RESULTS Scientists publish their results and conclusions in scientific journals, present at conferences, share with colleagues etc. Other scientists can verify the results by repeating the same experiment.

THEORY A Theory is hypothesis that is supported by a large body of scientific evidence obtained by many scientists over time. Theories can be revised. e.g. Theory of Evolution, The Cell Theory

LAWS Certain facts of nature are called laws. e.g. Law of Gravity, Law of Thermodynamics, Law of Elasticity (these can be written in an equation).