1. Variables and Hypothesis

2. Variable
What is it?
Variable: something that can change in an experiment. Most commonly known as the factor/thing being tested in the experiment.

3. Example
The time it takes to run a kilometer depends on the amount of exercise a person gets.
What are the variables?
amount of exercise
time to run a km
***Must include how each variable is measured or described!!!

4. Example
The higher the temperature of water, the faster an egg will cook.
What are the variables?
temperature of water
time it takes an egg to cook

5. Types of Variables Independent/Manipulated Variable (IV):
variable that is deliberately changed in order to test it (in most lab situations, you are changing this variable on purpose)
Dependent/Responding Variable (DV):
changes as a result of the manipulated variable: usually a measured change or visually observed change

6. Example The more you water the grass, the taller it will grow. IV DV
amount of water DV
height of the grass

7. Example
More bushels of potatoes will be produced if the soil is fertilized more. IV
amount of fertilizer DV
bushels of potatoes produced

8. Types of Variables Control Variable (CV):
A variable that is NOT changed. It is kept the same throughout and is often the most NORMAL situation. You compare the MV results to the CV results.

9. Identify and Control the Variable
The Control Group is a group whose conditions are not being changed.
The Experimental
Group is the group
whose conditions are
being changed.

10. Students of different ages are given the same puzzle to assemble
Students of different ages are given the same puzzle to assemble. The puzzle assembly time is measured. IV
age of student DV
time it takes to assemble the puzzle CV
puzzle (same)

11. Students of different ages are given the same puzzle to assemble
Students of different ages are given the same puzzle to assemble. The puzzle assembly time is measured.
Tables:
When creating data tables and graphs, the placement of the IV and DV is important.
Title: Time to assemble a puzzle based on age
IV = Columns (student age in years) 5 10 20
DV = Rows (time to assemble puzzle in minutes) 1

12. Students of different ages are given the same puzzle to assemble
Students of different ages are given the same puzzle to assemble. The puzzle assembly time is measured.
Graph
X axis IV
Y axis DV
Time in Minutes
Age of Students

13. Hypothesis Hypothesis
possible explanation for a set of observations or an answer to a scientific question.
Based on a person’s observations and previous knowledge or experience.
Hypotheses must be testable through an investigation.

14. How to Write a Hypothesis
If the independent variable changes then the dependent variable changes .
Always write your hypothesis in the third person (no I or you statements).

15. Practice! Write a hypothesis based on this question:
What is the relationship between free seating at lunch and the cleanliness of the tables?

16. More Practice!
What is the relationship between eating candy in science and good behavior?