1. THREE KINDS OF VARIABLES
EQ: What are the most effective ways to carry out a scientific inquiry?

2. Variables Sometimes in science, things are so big
like the size of the universe
or so small
like the movement of Euglena
that it is impossible for our brains to understand them in their entirety.

3. Variables
The scientific approach to understanding these events is a process that breaks down complex events into smaller pieces that can be studied and understood.
These smaller parts are called variables.

4. Variables
Variables are factors, conditions, and/or relationships that can change or be changed in an event or system

5. Three Kinds of Variables
In a scientific inquiry there are 3 kinds of variables:
Independent
Dependent
Controlled

6. Independent Variable
This is the factor or condition that is intentionally changed.
May only have one in a valid experiment!!!!
EX: A study was done to find if different tire treads affect the braking distance of a car.
I Variable: tire treads

7. Dependent Variable
This is the factor or condition that might be affected as a result of the change.
EX: A study was done to find if different tire treads affect the braking distance of a car.
D Variable: braking distance

8. Controlled Variable These are the variables that should not change.
Not necessarily mentioned in a description or hypothesis.
EX: A study was done to find if different tire treads affect the braking distance of a car
Controls: same car, new brake pads each time, same speed, same place applying brakes…

9. Practice 1: T-P-S
Two groups of students were tested to compare their speed working math problems. One group was given calculators, the other was not. Each group was given the same math problems.
I Variable:
D Variable:
Controls:

10. Practice 1 Independent Variable: Use of calculators
Dependent Variable: Speed computing the problems
Controls: same problems, same kids…

11. Practice 2: T-P-S
Students of different ages were given the same puzzle to complete. The puzzle assembly time was measured.
I Variable:
D Variable
Controls:

12. Practice 2 Independent Variable: Age of students
Dependent Variable: Speed of puzzle assembly
Controls: same puzzle

13. Sample Inquiry Discuss you research findings with your group.
What did you learn about variables that will help a paper airplane fly further/carry more cargo?
Come to a consensus as to which 3 distinct variables you will be testing in the coming weeks
Long wings, short wings, medium wings becomes length of wings, and counts as one variable, and your group needs to find two more variables
Open your log book to the NEXT blank page, and label it “VARIABLES”
Number the page, and add to your Table of Contents
p. ____ Variables

14. Sample Inquiry On the page labeled “VARIABLES”, label as follows
Independent Variable 1:
Independent Variable 2:
Independent Variable 3:
Dependent variable: length of flight (7th )
# of paperclips carried (8th)
Controls:

15. Sample Inquiry
Fill in your group’s information in the appropriate place in your log book
You should have MANY controls
Sample controls (but you are not limited to this list): force of throw, height of throw, person throwing, location ….

16. Writing Hypotheses
EQ: What are the most effective ways to carry out a scientific inquiry?

17. What is a real hypothesis?
A hypothesis is a tentative statement that proposes a possible explanation to some phenomenon or event.
Tentative: not certain or fixed
A tentative conclusion
A useful hypothesis is a testable statement which includes a prediction.

18. When are hypotheses used?
The key word is testable.
That is, you will perform a test of how two variables (independent and dependent) might be related.
This happens when you are doing the experiment.
When you are doing an experiment, you are testing a hypothesis.

19. When are hypotheses used?
Usually, a hypothesis is based on some previous observations.
Such as noticing that in November many trees undergo color changes in their leaves and the average daily temperatures are dropping.
Are these two events connected?
How?

20. How are hypotheses written?
Cooler days in November may cause the leaves on the trees to change color
Another example:
Dawn dish soap may blow bigger bubbles than a store brand
All of these are examples of hypotheses because they use the tentative word "may.".

21. How are formalized hypotheses written?
However, their form is not particularly useful. Using the word may does not suggest how you would go about proving it.
If these statements had not been written carefully, they may not have even been hypotheses at all.
For example, if we say "Trees will change color when it gets cold.“, we are making a prediction.
Or if we write, "Dawn dish soap will blow bigger bubbles than store brand soap”, this could be a conclusion.
One way to prevent making such easy mistakes is to formalize the form of the hypothesis by using the words, if and then.

22. Formalized Hypotheses
If leaf color change is related to temperature , then exposing plants to low temperatures will result in changes in leaf color.
Notice that these statements contain the words if and then.
They are necessary in a formalized hypothesis.
If you always ask yourself that if one thing is related to another, then you should be able to test it.

23. Formalized Hypotheses
Formalized hypotheses contain two variables.
One is independent and the other is dependent.
The independent variable is the one you, the scientist control
The dependent variable is the one that you observe and/or measure the results.

24. Formalized Hypotheses
But not all if-then statements are hypotheses.
For example, "If I play the lottery, then I will get rich."
This is a simple prediction.
In a formalized hypothesis, a tentative relationship is stated. For example, if the frequency of winning is related to frequency of buying lottery tickets.

25. Practice: T-P-S
A study was done to find if different tire treads affect the braking distance of a car.
Independent:
Dependent
Hypothesis --- Make sure a relationship between the I and D variables is clear

26. Sample Inquiry As a group, look at the variables you will be testing.
How do you predict your variables will cause your paper airplane to fly further/carry more cargo?
As a group, write a testable hypothesis in the if, then format, using your graphic organizer as a guide.
When you have one that you believe is testable, call Mrs. Belaski over to check.
Turn to the next blank page in your log book, number it, and title it: HYPOTHESIS
Turn to your table of contents. Add the Hypothesis in the appropriate place
Write your hypothesis in your log book.