1. Identifying
Variables

2. Let’s Review…. 6 steps of the Scientific Method?
Identify the Problem
Research
Hypothesis
Experiment
Data Analysis
Conclusion

3. Today’s Focus
Step 4- EXPERIMENT

4. Designing a valid experiment is easy- once you identify your variables!

5. A variable is something that changes.

6. What variables affect the taste of a chocolate chip cookie?
Example:
What variables affect the taste of a chocolate chip cookie?

7. Cookie Variables Recipe Amount of ingredients
Brands of ingredients used
Baking time
Oven temperature
Type of oven
Type of cookie sheet

8. 1 variable in an experiment!
You can only test
1 variable in an experiment!
Once you decide what you want to test, you must determine how to manage everything else.

9. Independent Variable Dependent Variable “Constant” Variables
3 Types of Variables
Independent Variable
Dependent Variable
“Constant” Variables
(aka Constants)

10. the variable that is changed on purpose by the experimenter
independent variable
the variable that is changed on purpose by the experimenter
aka cause, stimulus, reason, manipulated variable, what you are testing etc.
This is the ‘’if” part of a hypothesis.

11. the variable that responds
dependent variable
the variable that responds
aka effect(s), result(s), responding variable, etc.
This is the ‘’then” part of a hypothesis.

12. constants
all other variables that are NOT allowed to change during the experiment

13. 3 Concepts for Valid Experiments
Control Group
Treatment Group
Repeated Trials

14. control group the group (standard) to which everything is compared
(this group doesn’t actually do the experiment!!)

15. the group(s) being tested with the independent variable
treatment group
the group(s) being tested with the independent variable
*This group actually does the experiment!*

16. the number of times the experiment is repeated
repeated trials
the number of times the experiment is repeated
The more times you repeat the experiment, the more VALID your results are.

17. helps you design an experiment.
IVCDV
The
chart
helps you design an experiment.

18. Problem: how does fertilizer affect plant growth??

19. These are the fertilizer amounts varied by the experimenter.iv
constants dv
fertilizer
The variable (factor) that you will change is the independent variable.
0 drops
These are the fertilizer amounts varied by the experimenter.
2 drops
4 drops
6 drops

20. iv
constants dv
fertilizer
plant growth
0 drops
The variable (factor) resulting from the independent variable is the dependent variable.
2 drops
4 drops
6 drops

21. iv
constants dv
fertilizer
amt. of water
plant growth
type of soil
0 drops
These are the factors that must NOT change during experimentation. They must remain constant.
amt. of soil
2 drops
type of plant
4 drops
type of planter
6 drops
size of planter
type of light
location

22. 6 drops fertilizer
4 drops fertilizer
2 drops fertilizer
no fertilizer

23. EXPERIMENTAL GROUP CONTROL 2 drops fertilizer 4 drops fertilizer
What is this called?
What are these called?
CONTROL
EXPERIMENTAL GROUP
no fertilizer

24. What are these called?
CONSTANTS

25. dependent variable What is this called?
The plant growth that you observe here can be called . . .
 the results (of adding fertilizer)
 the response (to adding fertilizer)
dependent variable
 the effects (of adding fertilizer) 2 4 6

26. Type of soil becomes the IV.
What do you do if you want to test the type of soil instead of fertilizer? iv dv
constants
plant growth
fertilizer
amt. of water
type of plant
type of planter
size of planter
amt. of soil
type of light
location
type of soil
type of soil
fertilizer
Type of soil becomes the IV.
Fertilizer becomes a constant.

27. In the following two slides, identify the
independent variable
constants
dependent variable.

30. Evaluate the experimental design in the next two slides.

33. Let’s Practice ID’ing Variables
All types…not specific types just yet

34. HW: V.P. 1
You are ID’ing specific types of variables
(IV, C, DV)