Types of Variables Poster
What Is a Variable?
A variable is any element that can be changed in a science experiment. This could be something
like a factor, characteristic, amount, colour, size, location or condition.
Colour
Size
Shape
Quantity
There are three main types of variables in an investigation or experiment.
Independent Variable
Controlled Variables
This is the variable that the scientist intentionally changes.
These are all the variables that
we keep the same to ensure
that the experiment is a fair
test. They are all the variables
that we will keep constant
throughout the investigation so
that we can measure the change
of the independent variable on
the dependent variable.
Dependent Variable
This is the variable that is measured.
In other words, when we change the independent variable,
we are measuring what happens to the dependent variable.
Example
1 metre
0.5 metres
0.15 metres
An investigation tests the effect that the distance between light source and plant has on the growth of
a plant. The variables in this experiment would be the following:
Independent variable: The distance between the light source and the plant.
Dependent variable: The effect on the plant growth. Remember this must be measurable! You
could measure something such as (but not limited to): the height of the plant, the number of
leaves, or the number of disease spots present.
Controlled variables: To ensure that this is a fair test, you need to keep some aspects of the
experiment the same. This includes (but is not limited to): the type of plant, the size and type of pot,
the type and amount of soil, the amount and quality of water received and the amount of time in light.