Variable review
Independent, dependent, and controlled variables
Independent variable
What is changed
The factor deliberately changed between experimental conditions.
Dependent variable
What is measured
The response measured or observed during the investigation.
Controlled variables
What is kept constant
Factors maintained consistently to support a fair comparison.
Student information
Worksheet details
Practice scenarios
Identify the experimental variables
Plant growth and light
A student places identical plants under different numbers of hours of light each day and measures their height after three weeks.
Independent variable
Dependent variable
Controlled variables
Water temperature and dissolving time
A student measures how long the same mass of sugar takes to dissolve in water at different temperatures.
Independent variable
Dependent variable
Controlled variables
Ramp height and travel distance
A toy car is released from different ramp heights, and the distance traveled across the floor is measured.
Independent variable
Dependent variable
Controlled variables
Fertilizer concentration and leaf number
Plants receive different fertilizer concentrations while water, soil, pot size, and light are kept constant.
Independent variable
Dependent variable
Controlled variables
Exercise duration and heart rate
A student exercises for different lengths of time and records heart rate immediately afterward.
Independent variable
Dependent variable
Controlled variables
Surface area and reaction rate
Equal masses of a solid are used in different particle sizes, and the reaction time is measured.
Independent variable
Dependent variable
Controlled variables
Create your own
Design a variable-based investigation
Write an investigation question
Independent variable
Dependent variable
Controlled variables
How will the result be measured?
Final review
Variables identification checklist
- Only one main factor is deliberately changed.
- The measured response is clearly defined.
- Measurement units are identified.
- Important conditions are kept constant.
- The procedure allows a fair comparison.
- The investigation question is testable.
Related resources
Continue planning the investigation
Review the Experimental Variables Guide, plan the method with the Experiment Planning Template, and strengthen comparisons using the Control and Experimental Groups Guide.
Questions and answers
Experimental variables worksheet FAQ
What is an independent variable?
The independent variable is the factor deliberately changed by the investigator.
What is a dependent variable?
The dependent variable is the factor measured or observed in response to the independent variable.
What are controlled variables?
Controlled variables are factors kept constant so that the effect of the independent variable can be evaluated fairly.
Can an experiment have more than one dependent variable?
An investigation may measure more than one response, but each dependent variable should be defined and recorded clearly.