VariablesVariables

• What types of variables effect an experiment?

• How can you identify each type of variable?

Essential questions:

Variables

Variables: things that change

Variables

In any experiment there are 3 variables:

an independent (or input) variable

a dependent (or outcome) variable

some control variables

Let’s look at each type….

Variables

Independent variable: The thing you decide to change.

Example 1

You decide the weight to apply, so:

Weight is the independent variable.

Investigating how a weight affects the length of an elastic band.

Variables

Dependent Variable: the variable that changes as a result of changing the independent variable.

This is the variable you measure

Example 1

You measure the resulting length of the elastic band, so:

Length is the dependent variable.

Investigating how a weight affects the length of an elastic band.

Variables

Controls: These are all the variables that must not change, to make sure it is a fair test.

Example 1

You must use the same elastic band all the time, and the same scale etc,so it is a fair test.

Investigating how a weight affects the length of an elastic band.

Variables

Example Experiment:

How does the starting temperature of a beaker of water affect the time the beaker will take to cool down?

Example:

Imagining this experiment, write down the : Independent variable:

Dependent variable:

Control variables

Example

Remember, the dependent variable is what changes as a result of your experiment, it’s the variable you measure, so…

You measure TIME, so:

Time the beaker takes to cool down is the dependent variable.

Question: How does the starting temperature of a beaker of water affect the time the beaker will take to cool down?

Example

Remember, the independent variable is what YOU change, so…

You change the starting temperature, so:

STARTING TEMP is the independent variable.

Question: How does the starting temperature of a beaker of water affect the time the beaker will take to cool down?

Example

Remember, the control variables are all the variables that must not change, to make sure it is a fair test.

You must use the same beaker, with the same amount of water, in the same position in the room, at the same room temperature,so it is a fair test.

Question: How does the starting temperature of a beaker of water affect the time the beaker will take to cool down?

Example:

Imagining this experiment, write down the : Independent variable:

Starting temperature

Dependent variable:

Time to cool

Control variables

Same beaker, amount of water, room temp

When you draw up a table of your results,

the independent variable goes in the first column, like this:

Tables

If you take several readings of the dependent variable, then you can calculate the mean (average)Then your results will be more reliable.

Groups

The experimental group: the group in a scientific experiment where the experimental procedure is performed

The control group is a group that does NOT get the experimental procedure.