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.