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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: