Hypothesis-Based Science & Experimental Design
Inspiration for Hypotheses Scientists have to be inspired by the world around them to form hypotheses. Observations Questions Hypotheses
Hypothesis Formation A hypothesis is an educated guess that states a cause and effect relationship that is believed to exist in nature (a scientific inference) A suggested, testable answer to a well- defined scientific question It is often written in the form of an “If…, then” statement
Example Hypothesis In the Russian Psychic experiment, “If the psychic uses his powers, then the test subject’s blood pressure and brain waves will change from normal.
Experimentation To determine if the cause and effect relationship really exists, the researcher has to manipulate the cause and measure the effect.
The Cause The cause is experimentally referred to as the independent variable Thus, the researcher Manipulates the Independent Variable In the Russian Psychic experiment, the independent variable was represented by the three 15 minute period when the psychic was told to try to effect the blood pressure or brain waves of the subject.
The Effect The effect is the dependent variable Thus, the researcher Measures the Dependent Variable In the Russian Psychic experiment, the dependent variable was measured when the blood pressure or brain waves of the subject were taken.
A Phrase to Remember Manipulate the Independent Variable (cause) and Measure the Dependent Variable (effect)
Experimental Groups 1.Experimental Group (or period) This group includes test subjects receiving the manipulated form of the independent variable In the Russian Psychic experiment, it was the 3 test when the psychic was trying to effect the blood pressure or brain waves of the subject.
Control Group 1.Control Group This group includes test subjects when they are not being manipulated. This is the normal condition that is used to compare the experimental condition to. In the Russian Psychic experiment, it was the 1 test when the psychic was not trying to effect the subject.