1. Quick Write
What is a control group?

2. Scientific Method - Controls and Variables

3. Scientific Experiments Follow Rules.
An experimenter changes one factor and observes or measures what happens.
An experimenter always has a control

4. What is the Purpose of a Control?
Controls are NOT being tested
Controls are used for COMPARISON

5. What are Variables?
A variable is any factor trait or condition that can exist in differing amounts or types.
There are 3 types of variables we will look at.

6. 1. The Control Variable
The experimenter makes a special effort to keep other factors constant so that they will not affect the outcome.
Those factors are called control variables.

7. 2. Independent Variable
The factor that is changed is known as the independent variable.
In data tables, this variable will be on the left side.
When we graph, this variable will go on the y-axis.

8. 3. Dependent Variable
The factor that is measured or observed is called the dependent variable. .
In data tables, this variable will be on the right side.
When we graph, this variable will go on the x-axis.

9. Let’s Practice!!!
Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, they're supposed to staple a set of papers). Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks.

10. Independent Variable – Dependent Variable – Control – Conclusion –
Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, they're supposed to staple a set of papers). Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks.
Problem –
Hypothesis –
Independent Variable –
Dependent Variable –
Control –
Conclusion –
What will increase the productivity of the workers?
If workers drink the special juice, then their productivity will increase.
The special juice
Increased productivity
Group B, did not get special juice
Smithers’ s results did not support his hypothesis. The group (A) that received the special juice only made 1,587 stacks. The control group (B) made 2,113 stacks.

11. What are some things he should keep constant?

12. Independent Variable – Dependent Variable – Control – Conclusion –
Homer notices that his shower is covered in a strange green slime. His friend Barney tells him that coconut juice will get rid of the green slime. Homer decides to check this out by spraying half of the shower with coconut juice. He sprays the other half of the shower with water. After 3 days of "treatment" there is no change in the appearance of the green slime on either side of the shower.
Problem –
Hypothesis –
Independent Variable –
Dependent Variable –
Control –
Conclusion –
Constants?
What will remove the green slime from the shower?
If coconut juice and plain water are sprayed on the shower, then the coconut juice will remove the green slime.
The coconut juice
The amount of slime
The plain water
Homer’s results did not support his hypothesis. The coconut juice did not remove the green slime.

13. Independent Variable – Dependent Variable – Control – Conclusion –
Bart believes that mice exposed to microwaves will become extra strong (maybe he's been reading too much Radioactive Man). He decides to perform this experiment by placing 10 mice in a microwave for 10 seconds. He compared these 10 mice to another 10 mice that had not been exposed. His test consisted of a heavy block of wood that blocked the mouse food. He found that 8 out of 10 of the microwaved mice were able to push the block away. 7 out of 10 of the non-microwaved mice were able to do the same.
Problem –
Hypothesis –
Independent Variable –
Dependent Variable –
Control –
Conclusion –
Will exposing mice to microwaves make them stronger?
If the mice are exposed to microwaves, then they will become stronger.
Exposing the mice to microwaves
The strength of the mice
The mice not exposed to the microwaves
Bart’s results were inconclusive. Although the group exposed to the microwaves did perform better, it was only by one mouse. Other variables could have caused the results.

14. Independent Variable – Dependent Variable – Control – Conclusion –
Krusty was told that a certain itching powder was the newest best thing on the market, it even claims to cause 50% longer lasting itches. Interested in this product, he buys the itching powder and compares it to his usual product. One test subject (A) is sprinkled with the original itching powder, and another test subject (B) was sprinkled with the Experimental itching powder. Subject A reported having itches for 30 minutes. Subject B reported to have itches for 45 minutes.
Problem –
Hypothesis –
Independent Variable –
Dependent Variable –
Control –
Conclusion –
Will the new itching powder last longer than the original itching powder?
If both itching powders are tested, then the new itching powder will produce longer lasting itches.
The new itching powder (B)
How long the itches last
The original itching powder (A)
Krusty’s results support his hypothesis. The group that received the new itching powder experienced itches that lasted for 45 minutes, 50% longer than the control group.

15. Krusty Krabs Breath Mints
Mr. Krabs created a secret ingredient for a breath mint that he thinks will “cure” the bad breath people get from eating crabby patties at the Krusty Krab. He asked 100 customers with a history of bad breath to try his new breath mint. He had fifty customers (Group A) eat a breath mint after they finished eating a crabby patty. The other fifty (Group B) also received a breath mint after they finished the sandwich; however, it was just a regular breath mint and did not have the secret ingredient. Both groups were told that they were getting the breath mint that would cure their bad breath. Two hours after eating the crabby patties, thirty customers in Group A and ten customers in Group B reported having better breath than they normally had after eating crabby patties
What is Mr. Krabs’ problem?
What should Mr. Krabs’ hypothesis be?
Which group is the control group?
What is the independent variable?
What is the dependent variable?
What should Mr. Krabs’ conclusion be?
Why do you think 10 people in group B reported fresher breath?
How can customer’s bad breath be cured?
If customers eat the breath mint with the secret ingredient, then they will have better breath
Group B, who received the regular breath mint
The secret ingredient
Amount of bad breath
Mr. Krabs’ results support his hypothesis. 30 out of 50 of the people who received the secret ingredient reported better breath, 20 more than the control group.
The placebo effect. Since both groups were told they were receiving the secret ingredient, the placebo effect could have made them think they had better breath.

16. Time to Self-Assess 5 – Mastered it! 4 – Own it! 3 – Getting there!
Learning Goal:
Recognize the steps to the scientific method
and demonstrate how to use them to solve a
problem
Time to Self-Assess
5 – Mastered it!
4 – Own it!
3 – Getting there!
2 – Confused!
1 – No clue!