1. Identifying Variables & Designing Investigations

2. 3 Kinds of Variables
Independent Variable – something that is changed by the scientist
What is tested
What is manipulated
The cause or stimulus

3. 3 Kinds of Variables
Dependent Variable – something that might be affected by the change in the independent variable
What is observed
What is measured
The data collected during the investigation
The result or response

4. 3 Kinds of Variables
Controlled Variable – a variable that is not changed
Also called constants
Allow for a “fair test”

5. For Example:

6. Students of different ages were given the same jigsaw puzzle to put together. They were timed to see how long it took to finish the puzzle.

7. Identify the variables in this investigation.

8. Match the variable with the statement:
The time it took to put the puzzle together.
Independent variable
Dependent variable
Controlled variable

9. Match the variable with the statement:
The time (observed and measured by the scientist) it took to put the puzzle together.
Independent variable
Dependent variable
Controlled variable

10. Match the variable with the statement:
The same jigsaw puzzle.
Independent variable
Dependent variable
Controlled variable

11. Match the variable with the statement:
The same jigsaw puzzle.
Independent variable
Dependent variable
Controlled variable

12. Match the variable with the statement:
The ages of the students (different ages were tested by the scientist).
Independent variable
Dependent variable
Controlled variable

13. Match the variable with the statement:
The ages of the students (different ages were tested by the scientist).
Independent variable
Dependent variable
Controlled variable

14. Another example:

15. An investigation was done with an electromagnetic system made from a battery and wire wrapped around a nail. Different sizes of nails were used. The number of paper clips the electromagnet could pick up was measured.

16. What are the variables in this investigation?

17. Match the variable with the statement:
The sizes of the nails (changed by the scientist).
Independent variable
Dependent variable
Controlled variable

18. Match the variable with the statement:
The sizes of the nails (changed by the scientist).
Independent variable
Dependent variable
Controlled variable

19. Match the variable with the statement:
The number of paper clips picked up (observed & counted by the scientist).
Independent variable
Dependent variable
Controlled variable

20. Match the variable with the statement:
The number of paper clips picked up (observed & counted by the scientist).
Independent variable
Dependent variable
Controlled variable

21. Match the variable with the statement:
The battery, wire, and type of nail (none of these items were changed).
Independent variable
Dependent variable
Controlled variable

22. Match the variable with the statement:
The battery, wire, and type of nail (none of these items were changed).
Independent variable
Dependent variable
Controlled variable

23. One more:

24. The higher the temperature of water, the faster an egg will boil.

25. Independent variable –
Controlled variable –

26. Independent variable – temperature of water
Dependent variable – time to cook an egg
Controlled variable – type of egg

27. Last one:

28. The temperature of water was measured at different depths of a pond.

29. Independent variable –
Controlled variable –

30. Independent variable – depth of the water
Dependent variable – temperature
Controlled variable – thermometer

31. Designing Investigations

32. The greater the amount of soap in a soap and water mixture, the bigger a soap bubble can be blown.
Design an investigation to test this hypothesis.
Identify the variables
What exactly will be changed? How will it be changed?
What exactly will be measured? How will it be measured?

33. The farther a ball drops, the higher it will bounce.
Design an investigation to test this hypothesis.
Identify the variables
What exactly will be changed? How will it be changed?
What exactly will be measured? How will it be measured?