Unit 1: Science in Action 9/19/12 Objective: SWBAT discern the difference between controls and variables Vocabulary: independent, dependent, variable, control Initial Activity: Write an I (inference) or O (Observation) next to the following statements. ___ The man in the drugstore fell on the floor ___ Even though Jennifer didn’t say anything at the party, I could tell she was having a great time ___ The elephants ate 5 pounds of hay today ___ Jason stared at the computer screen for 10 minutes

3 Kinds of Variables  Independent Variable – something that is changed by the scientist  What is tested  What is manipulated

3 Kinds of Variables  Dependent Variable – something that might be affected by the change in the independent variable  What is observed  What is measured  The data collected during the investigation

3 Kinds of Variables  Controlled Variable – a variable that is not changed  Also called constants  We don’t test the constant so we have something to compare our data too.

Example of Controls & Variables 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.

What are the Variables in Your Experiment? Varying the route is the independent variable Varying the route is the independent variable The time it takes is the dependent variable The time it takes is the dependent variable Keeping the same walker throughout makes the walker a control variable. Keeping the same walker throughout makes the walker a control variable.

One more thing… it is best to make several trials with each independent variable.

Follow up…. Complete the “Identifying Variables” activity independently. To be handed in at the end of class Closing: Share out and review answers Homework Complete the Simpsons Variables/Constants activity.

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.

The Control Variable The experimenter makes a special effort to keep other factors constant so that they will not effect the outcome. The experimenter makes a special effort to keep other factors constant so that they will not effect the outcome. Those factors are called control variables. Those factors are called control variables.

What is the Purpose of a Control?  Controls are NOT being tested  Controls are used for COMPARISON