1. Independent, Dependent, Constant
Variables
Independent, Dependent, Constant

2. Types of variables Constant
(and Control… we will review this at the end)

3. Types of variables
Constant

4. Design an Experiment about… Plants

5. Design an Experiment About… Plants
What would be our dependent variable? What can we measure?
How tall the plant grows
How fast the plant grows
The mass of the plant
The size of the leaves
The colour of the plant

6. Dependent Variable Our dependent variable is (pick ONE):
How fast the plant grows
Dependent variable: something you can’t control directly, but you can observe and measure

7. Types of variables
Constant

8. Design an Experiment About… Plants
What would be our independent variable? What can we change?
The amount of water we give the plant
The type of water we give the plant (salt water)
The amount of sunlight the plant receives
The amount of fertilizer (compost)
The type of soil we use
The amount of soil we use
The type of plant
The amount of nutrients we give the plant
The temperature
The depth you plant the seed
The size of the seed you plant

9. Independent Variable Our independent variable is (pick ONE):
The amount of fertilizer we give the plant
Independent variable: something you are manipulating during your experiment, this will affect the dependent variable

10. Our variables are...
Independent variable: The amount of fertilizer we give the plant
Dependent variable: How fast the plant grows
(You could have picked different variables from the list… there are usually LOTS of different options for variables! But for each experiment you will pick ONE VARIABLE to study.)

11. Purpose of the Experiment
Independent variable Dependent variable
Independent variable: The amount of fertilizer we give the plant
Dependent variable: How fast the plant grows

12. Purpose of the Experiment
Independent variable Dependent variable
How will the amount of fertilizer we give the plant affect how fast the plant grows?

13. Hypothesis Independent variable Dependent variable
BECAUSE _______________________________________________.
Independent variable: The amount of fertilizer we give the plant
Dependent variable: How fast the plant grows

14. Hypothesis
Independent variable: The amount of fertilizer we give the plant
Dependent variable: How fast the plant grows
IF we give the plant fertilizer THEN the plant will grow faster BECAUSE the fertilizer will provide the plant with more nutrients.

15. Types of variables
Constant: variables that stay the same, what you don’t change

16. Constant Variables
How do we find our constant variables? Look at the list we came up with for independent variables.
We picked ONE variable as our independent variable. This is the variable we are manipulating.
Every other variable on the list… needs to stay constant (stay the same).
Constant variable: things that you are NOT changing, they stay the same for everything in your experiment

17. Constant Variables Our constant variables are:
The amount of water we give the plant
The type of water we give the plant (salt water)
The amount of sunlight the plant receives
The type of soil we use
The amount of soil we use
The type of plant
The amount of nutrients we give the plant
The temperature
The depth you plant the seed
The size of the seed you plant

18. Constant Variables
We want to know: How will the amount of fertilizer we give the plant affect how fast the plant grows?
Example: we will keep the amount of water we give the plant constant. We will give all plants exactly the same amount of water.
Why…? Our experiment is looking for the effects of fertilizer. If we change any other variables, we can’t tell what results are from the fertilizer! So everything else stays CONSTANT.

19. Control Control group: does not get the variable that is being tested
Is the “opposite” of your hypothesis
Example: our hypothesis is... if we give the plant fertilizer then…
Opposite: If we DON’T give the plant fertilizer…
Control group: plants that don’t get fertilizer