This document defines variables and their types in scientific experiments. An independent variable is the condition intentionally changed by the investigator. A dependent variable is what is measured and can change as a result of the independent variable. Controlled variables are kept the same in an experiment. Examples are provided of identifying the independent, dependent, and controlled variables for experiments on how temperature affects ball bounce height, how light color affects plant growth rate, and how parachute size affects time for a hippo to fall 10 feet.

1. What is a Variable?

2. DEFINITION
Variable – Any factor that
can change in a scientific
investigation or
experiment

3. Types of Variables
Independent Variable
The condition that is intentionally
changed by the investigator in an
experiment
There can be only one independent
variable in an experiment

4. Dependent Variable
 The factors or conditions that will change
as a result of the independent variable
The factors that you measure or observe as
data
There can be one or more dependent
variables in an experiment
Types of Variables

5. Controlled Variables
The factors or conditions that are
kept the same (unchanged) in an
experiment.
There are many controlled variables
in an experiment
Types of Variables

6. Identify variables for the
following experiments.
You can do it!
Practice

7. • Does changing the temperature
of a ball affect the height the
ball will bounce?
Testable Question #1
HotCold

8. Manipulated
Variable
Responding
Variable
Identify Variables #1
Cold Hot
• Does changing the temperature
of a ball affect the height the ball
will bounce?

9. • Controlled Variables:
* Same ball
* Dropped from the same height
* Dropped onto the same surface
* etc…
Identify Variables #1

10. • Does changing the color of light
affect the growth rate of plants?
Testable Question #2

11. Manipulated
Variable
Responding
Variable
Identify Variables #2
• Does changing the color of light
affect the growth rate of plants?

12. • Controlled Variables:
* Same type / size of plant
* Same wattage of bulb
* Same amount of water
* Same soil
* Light on for the same amount of
time
* etc…
Identify Variables #2

13. • How does the size of a parachute
affect the time it takes a
hippo to fall 10 feet?
Testable Question #3

14. Manipulated
Variable
Responding
Variable
Identify Variables #3
• How does the size of a parachute
affect the time it takes a hippo to
fall 10 feet?

15. • Controlled Variables:
* Same hippo
* Dropped from the same height
* Same parachute fabric
* Same length of strings on the parachute
* etc…
Identify Variables #3