A variable is a factor in an experiment that can be changed.
When you set up an experiment in the correct way you need to think about control, independent and dependent variables.
What is an independent variable?
The independent variable is the factor changed in an experiment. There is usually only one independent variable as otherwise it’s hard to know which variable has caused the change.
What is a dependent variable?
The dependent variable is the variable measured in an experiment. It depends on the independent variable!
What is a control variable?
Control variables are variables that must be kept the same in an experiment.
Usually only one variable is measured and an experiment investigates how changing the independent variable affects the dependent variable.
Experiment ideas for learning about setting up a fair test
Investigating the effect of exercise on heart rate
If you wanted to investigate the effect of exercise on heart rate the variables would be as follows
Control variables
Same person exercising
Same method used to measure heart rate.
Independent variable
Type of exercise or no exercise.
Dependent variable
Heart rate
Investigating the effect of viscosity of a liquid on flow rate
If you wanted to investigate how the thickness of a liquid affects it’s flow rate the variables would be as follows.
Control variables
Gradient of ramp
Distance travelled by each liquid
Amount of each liquid used
Independent variable
Liquid used
Dependent variable
Time taken for each liquid to travel a set distance
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