1. Scientific Method – Experimental Design Controls and Variables

2. Scientific Experiments Follow Rules.
An experimenter changes one factor and observes or measures what happens.

3. The Control Variables
The experimenter makes a special effort to keep other factors constant so that they will not effect the outcome.
Keep them the same!

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

5. Other Variables
The dependent variable is what the investigator measures (or counts or records). It is what the investigator thinks will vary during the experiment. For example, you may want to study peanut growth. One possible dependent variable is the height of the peanut plants.

6. Name some other aspects of peanut growth that can be measured.

7. Other Variables
The independent variable is what the investigator deliberately varies during the experiment. It is chosen because the investigator thinks it will affect the dependent variable.
Name some factors that might affect the number of peanuts produced by peanut plants.

8. 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.

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

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