How Science works:

VariablesVariables

• About the different types of variables,

• How to identify them when doing your practical work.

Learning Objectives

You should learn :

Variables

Variables are things that

vary and change

Variables

In any experiment there are 3 variables:

some control variables

an independent variable

a dependent variable

Let’s look at each type….

Control variables

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

• Also called “constants”

Independent Variable

• This is the thing that you decide to change.

oWhat is tested

oWhat is manipulated

Dependent Variable

• This is the variable that changes as a result.

• It is the variable that you measure.

o What is observed

o What is measured

o The data collected during the investigation

Students of different ages were given the same jigsaw puzzle to put together. They were timed to see how long it took to finish the puzzle.

Example Situation

Identify the independent, dependent, and control variables.

Control Variables

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

• Same puzzle

• All of the participants were tested with the same puzzle

• It would not have been a fair test if some had an easy 30 piece puzzle and some had a harder 500 piece puzzle.

Independent (input) variable

This is the thing that you decide to change.

You decide the ages to be tested, so:

The ages of the students is the independent variable.

• The ages of the students

• Different ages were tests by the scientists

Dependent (outcome) variable

This is the variable that changes as a result.It is the variable that you measure.Which is the dependent variable here?• The time it took to put the

puzzle together

• The time was observed and measured by the scientist

The higher the temperature of water, the faster an egg will boil.

Another Example Situation

Identify the independent, dependent, and control variables.

Variables

Independent: the temperature of the water

Dependent: time needed to cook the egg

Controls: type of egg, stove, pots used

• Understand the difference between- independent, - dependent, and - control variables

• Be able to identify these variables when doing your practical work.

Learning Outcomes

You should now: