Control Variable

Key Stage 2

Meaning

A control variable is something which is kept the same in an experiment to make it a fair test.

About Control Variables

Changing more than one thing in an experiment can affect the results.

If you do not have control variables it is not a fair test.

Examples

This race would not be a fair test if variables were not controlled.

Investigation: Who is the fastest?	Controls
	Everyone starts from the same starting line. Everyone finishes at the same point. Everyone wears the same kind of shoes. Everyone has to run on the grass.

This race would not be a fair test if variables were not controlled.

Experiment: Does light affect cress growth?	Controls
	Everyone starts from the same starting line. Everyone finishes at the same point. Everyone wears the same kind of shoes. Everyone has to run on the grass.

If you want to know how plants grow differently depending on the light, you should make sure they are all watered the same, have the same soil and are kept at the same temperature.