1. The Scientific Method:
A look at the experimental variables and a hypothesis

2. What is an “experiment?
In school “experiment” often gets applied to any hands on activities.
We have not completed any true experiments so far this year.
We will have several hands on experiences but only a few experiments.

3. What is a true “experiment”?
A science experiment tests a hypothesis following a procedure or set of steps
In order to write a hypothesis you need to understand experimental groups and variables

4. Experimental Groups/Conditions
Manipulated group (M)
(aka manipulated condition)
Control group (C)
(aka control condition)
It is what you are testing to see if it has an effect
You test only one variable at a time
Has the manipulated variable applied to it
Sometimes called the test condition or group as well
The group that does not have the manipulated variable applied to it
Used to compare to the manipulated
If there is a difference between the manipulated and the control then the manipulated variable influenced the results

5. Does Miracle-Gro® make a plant grow taller?
Experimental Question:
Does Miracle-Gro® make a plant grow taller?

6. What would the experimental conditions be?
Manipulated Condition
Control Group
Applying Miracle-Gro® fertilizer to plants
Plants that do not have Miracle-Gro® applied to them

7. Experimental Variables
In order to set up the experimental groups you need to understand the variables:
Manipulated
Responding
Standardized (sometimes called controlled variables)

8. Manipulated Variable (MV)
This is what the experimenter changes to see if it has an effect
In the Miracle-Gro® experiment what is our manipulated variable?

9. Responding Variable (RV)
This is what you will measure
It is called the responding variable because it is the “response” you expect to get from the change you made
You can use both qualitative and quantitative observations to observe the response
What would the responding variable be?

10. Standardized Variables (SV)
These are all of the things that are kept the same between the test groups/conditions in the experiment
What should the standardized variables be in this experiment?

11. What is a hypothesis?
A prediction of what you think will happen as a result of the changes you made in the experiment:
Do you think the manipulated variable will have an affect?
How do you think it will affect the responding variable?

12. How to write a hypothesis
You need to write your hypothesis in an if, then, because statement

13. If….
The if part of your statement should explain to your reader the experiment setup. It needs to answer the following:
What is your manipulated group?
What is your control group?
Example: If we apply miracle grow fertilizer to half of the plants and no fertilizer to the others

14. Then….
The then part of your statement explains what you think will happen
You should explain what you expect to see in terms of the responding variable.
Example:Then the plants that have the fertilizer will grow taller than the plants that do not have fertilizer

15. Because… Your hypothesis should be an educated guess
The because part of the statement explains or justifies why you believe the experiment should turn out in this way
It should be based on prior knowledge or research
Example: Because miracle is advertised to make plants grow taller

16. Putting the parts together
If we apply miracle grow fertilizer to half of the plants and no fertilizer to the others Then the plants that have the fertilizer will grow taller than the plants that do not have fertilizer Because miracle is advertised to make plants grow taller