1. Identifying Variables
Scientific Method
Identifying Variables
Let’s say you are testing different colored lights on the rate of bean seed germination. To rephrase this, your problem is to germinate some bean seeds under different colors of light.

2. You are testing how color affects the rate of bean seed germination
You are testing how color affects the rate of bean seed germination. In other words, you will germinate bean seeds under different colors of light to see which one works the best.

3. So, if you are testing different colored lights on the germination of seeds, what is the one thing that you will change on purpose?
That will be the independent variable.

4. If you said that you will change the color of light, then you are correct.
The color of light used is the independent variable.

5. If you are testing different colored lights on the germination of bean seeds, what are you measuring?
This will be the dependent variable.

6. If you said that you will measure how long it takes the seeds to germinate, then good for you! That’s correct!

7. If you are testing different colors of light on the rate of bean seed germination, what would be some things that should stay the same?
These are called constants.

8. The following are all constants in the experiment and should not be changed. If you stated any of these, you are right!
type of seed
environment
type of soil
amount of soil
method of planting seeds
type of container
depth of seed
amount of water
type of water
amount of light

9. Finally, if you are testing different colors of lights on the germination of seeds, what is the control?
The control involves doing the experiment without the independent variable.

10. If you said that the control would be white light, then you are really thinking!
Taking away different colors just leaves plain white light.

11. You did it!
Try one more on your own. Pretend you want to know how caffeine affects the heart rate of middle school students. What would be the independent and dependent variables, constants and control?