Variables

Essential questions: What types of variables effect an experiment? How can you identify each type of variable?

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….

Weight is the independent variable. Variables Independent variable: The thing you decide to change. Example 1 Investigating how a weight affects the length of an elastic band. You decide the weight to apply, so: Weight is the independent variable.

Length is the dependent variable. Variables Dependent Variable: the variable that changes as a result of changing the independent variable. This is the variable you measure Example 1 Investigating how a weight affects the length of an elastic band. You measure the resulting length of the elastic band, so: Length is the dependent variable.

Variables Controls: These are all the variables that must not change, to make sure it is a fair test. Example 1 Investigating how a weight affects the length of an elastic band. You must use the same elastic band all the time, and the same scale etc, so it is a fair test.

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

Time the beaker takes to cool down is the dependent variable. Example Remember, the dependent variable is what changes as a result of your experiment, it’s the variable you measure, so… Question: How does the starting temperature of a beaker of water affect the time the beaker will take to cool down? You measure TIME, so: Time the beaker takes to cool down is the dependent variable.

STARTING TEMP is the independent variable. Example Remember, the independent variable is what YOU change, so… Question: How does the starting temperature of a beaker of water affect the time the beaker will take to cool down? You change the starting temperature, so: STARTING TEMP is the independent variable.

Example Remember, the control variables are all the variables that must not change, to make sure 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? 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.

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

Tables When you draw up a table of your results, the independent variable goes in the first column, like this: 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.