1. New Physics for You, pages 7 and 360
How Science works:
Variables
New Physics for You, pages 7 and 360

2. Learning Objectives
You should learn :
About the different types of variables,
How to identify them when doing your practical work.

3. Variables are things that vary and change

4. Variables In any experiment there are 3 variables:
an independent (or input) variable
a dependent (or outcome) variable
some constant (or control) variables
Let’s look at each type….

5. Independent (Manipulated) variable
This is the thing that you decide to change. There should only be one at a time.
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.

6. Independent (manipulated) variable
This is the thing that you decide to change.
Example 2
Investigating if a fertilizer will make beans grow better than just normal soil.
You decide to give the plants fertilizer,
So the fertilizer is the independent variable.

7. Dependent (Responding) variable
This is the variable that changes as a result. It is the variable that 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.

8. Dependent (responding) variable
This is the variable that changes as a result. It is the variable that you measure.
Example 2
Investigating if a fertilizer will make beans grow better than just normal soil.
You measure the growth of the bean plant, so:
Plant growth is the dependent variable.

9. Constant (control) variables
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.

10. Constant (Control) variables
These are all the variables that must not change, to make sure it is a fair test.
Example 2
Investigating if a fertilizer will make beans grow better than just normal soil.
You must use the same kind of beans, with the same amount of water, in the same amount of sunlight, at the same kind of soil, so it is a fair test.

11. same elastic band, same scale, etc, so it is a fair test.
In Summary
Example 1
The independent variable is ?
weight
The dependent variable is ?
length of the elastic
The control variables are ?
same elastic band, same scale, etc, so it is a fair test.

12. In Summary the fertilizer the growth of the plant
Example 2
The independent variable is ?
the fertilizer
The dependent variable is ?
the growth of the plant
The constant variables are ?
the same kind of beans, with the same amount of water, in the same amount of sunlight, at the same kind of soil, so it is a fair test.

13. Test Group
The group in the experiment that receives the independent variable
Their results tell you if the independent variable makes a difference

14. Control Group
The group in the experiment that doesn’t receive the independent variable
Their results tell you what would happen normally. It gives you something to compare your test data to.

15. Placebo Effect
When people in the control group get better because they think they are being treated.