1. The Iceman’s Last Journey
NOS Lesson 3
The Iceman’s Last Journey

2. A Controlled Experiment
What does it mean to have a controlled experiment?
 Everything is kept constant (the same) except the independent variable
If we change more than one variable, then we don’t know that the results are from the variable we are trying to test for!

3. First We Must Understand Variables!
Variable- any factor that can have more than one value
In controlled experiments there are 2 kinds of variables: _____________ and ____________ variables.
Independent
Dependent

4. The Independent Variable
The factor that you want to test.
It is changed by the investigator to observe how it affects a dependent variable
Example:
The amount of light each room of plants receives
Light Room
Dark Room

5. The Dependent Variable
The factor you observe or measure during an experiment
Example:
How high the plants grow
due to the amount of light
they are given
Light Room
Dark Room

6. When the independent variable is changed, it causes the dependent variable to change The dependent variable depends on the independent variable

7. A Controlled Experiment Has 2 Groups: The ______________ group and the ________ group
Experimental
Control

8. The Experimental Group
Used to study how a change in the independent variable changes the dependent variable
The “experiment” is happening on this group

9. The Control Group
Contains the same factors as the experimental group, but the independent variable is not changed
The group that stays the same so we can compare it to the experimental group

10. Why Do Scientific Experiments Require a Control Group?
Without a control, you can’t tell if your results (dependent variable) are from the variable you are testing (independent variable) or from another factor
We must have it to compare with the experimental group!

11. A Controlled Experiment Has:
Independent Variable
Dependent Variable
Experimental Group
Control Group