1. and the Controlled Experiment
Scientific Method
and the Controlled Experiment

2. Scientific Method: the steps scientist use in an investigation
Observation
Question
Hypothesis
Experiment
Data analysis
Conclusion
Communication

3. The Steps do not have to go in a certain order.
Follow the arrows on the diagram.
Notice different ways the process can take place.

4. An Observation is something you notice with your senses.

5. An Example of an Observation:
Every time my dog eats grass, he throws up.

6. Curious people have questions about their observation.
Does the grass make the dog throw up?
Or maybe the dog feels sick and the grass makes him feel better.
If I ate grass would it make me throw up?
How does grass make a dog throw up?
Why does the dog eat grass, if it makes him throw up?

7. Hypothesis: a possible answer to a question
Example of a Hypothesis:
It is possible that dogs eat grass because they need some green plants in their diet.

8. A good hypothesis can be tested with an experiment
In a controlled experiment, one factor is changed to observe the effect on another factor while all other factors are kept constant.

9. An Example of a Controlled Experiment:
Ten dogs of the same breed and age are fed the same amount of dog food each day.
Five of the dogs eat dog food containing vegetables and the other five eat dog food that is made of meat only.
All dogs are allowed outside in the grass for the same length of time each day.
All dogs are observed to see if they eat grass.

10. A variable is a factor that may change in an experiment.
There are two variables in a controlled experiment:
The independent variable
And the dependent variable

11. The independent variable is changed on purpose by the scientist.
What is the independent variable in the dog food experiment?
Vegetables in the dog food was the factor that was different in the two groups of dogs.

12. The Dependent Variable is measured or observed by the scientist to see if it was affected by the experiment.
What was the dependent variable in the dog food experiment?
Eating grass was measured or observed by the scientist to see if there was an affect on this behavior.

13. The constants in the experiment are kept the same so only one variable could affect the results of the experiment.
Can you list the constants in the dog food experiment?
Breed of the dog
Age of dog
Amount of dog food
Amount of time in the grass

14. To infer, is to draw a conclusion based on the results of the experiment.
The results of the experiment are analyzed.
The hypothesis is either accepted or rejected.
Then a conclusion can be made.

15. If there was no difference in the grass eating habits of the two groups of dog….
The hypothesis would be rejected and
the scientist might infer that a dog’s diet does not affect grass eating.

16. If the dogs that were on a diet that included vegetables ate less grass than the other dogs…….
The hypothesis would be accepted.
The scientist might infer that dogs eat grass because they need some plant material in their diet.

17. Communication
Scientists share their findings with each other by publishing papers that describe their work.