1

Scientific Method - Scientific Method - Controls and VariablesControls and Variables

2

Scientific Experiments Scientific Experiments Follow RulesFollow Rules..

• An experimenter changes one factor and observes or measures what happens.

3

The Control VariableThe Control Variable

• The experimenter makes a The experimenter makes a special effort to keep special effort to keep other other factors constantfactors constant so that they will so that they will not effect the outcome.not effect the outcome.

• Those factors called Those factors called control control variables.variables.

• Control variables Control variables are variables are variables that are not changed in an that are not changed in an experiment.experiment.

4

What is the Purpose of What is the Purpose of a Control?a Control?

•Controls are NOT being tested

•Controls are used for COMPARISON

5

Other Variables

•The factor that is changed is known as the independent variable.

• The factor that is measured or observed is called the dependent variable.

6

Example of Controls & Example of Controls & VariablesVariables

• For example, suppose you want to figure out the fastest route to walk home from school. You will try several different routes and time how long it takes you to get home by each one.

• Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.

7

What are the Variables What are the Variables in Your Experiment?in Your Experiment?

• Varying the route is the Varying the route is the independent variableindependent variable

• The time it takes is the The time it takes is the dependent variabledependent variable

• Keeping the same walker Keeping the same walker throughout makes the walker throughout makes the walker a a control variable.control variable.

8

One more thing… it is best to make several

trials with each independent variable.

9