Controlling Variables

Hypothesis

The hypothesis is an educated guess about the relationship between the

independent and dependent variables.

Let’s learn about the 3 types of variables!

The 3 types of variables!

Independent Variable• Independent Variable – the one thing that is

changed in an experiment–What is tested–What is manipulated

Dependent Variable• Dependent Variable: the variable that is

affected by the change in the independent variable–What is measured–What is observed– The data collected during the investigation– the factor that may change as a result of

changes made in the independent variable.

Controlled Variables• Constant: a variable that is not changed–Also called controlled variable–Allows for a “fair test”

• Control group: exposed to the same conditions as the experimental group, except for the variable being tested.

• Serves as the standard of comparison.• The control group may be a “no treatment" or

an “experimenter selected” group.All experiments should have

a control group.

Identify the variables:• Hypothesis: If we add more air, the ball will

bounce higher.– Independent variable:• the amount of air in the ball

– Dependent variable: • How high the ball bounces

– Controlled variables: • type of ball, drop the ball from the same height, drop the

ball on the same surface

Identify the variables:• Hypothesis: If a plant gets sunlight it will

grow taller.• Independent variable: – sunlight

• Dependent variable: – Growth of plants

• Controlled variable: – Type of plant, pot, dirt, water, location, fertilizer