1. Bellringer
What should you do if your data in your experiment is inaccurate or your experiment is flawed?
What step do you complete after you gather information?
What do we call a possible explanation, answer to a question or an educated guess?
What is data?

2. Identifying Variables & Designing Investigations

3. 3 Kinds of Variables
Independent Variable – something that is changed by the scientist the ‘I control’ variable
What is tested
What is manipulated

4. 3 Kinds of Variables
Dependent Variable – something that is affected by the change in the independent variable
What is observed
What is measured
The data collected during the investigation

5. 3 Kinds of Variables
Controlled Variable – a variable that is not changed
Also called constants
Allow for a “fair test”

6. In our math problems we used independent and dependent variables too!
Independent variable
(The one number we changed)
2+2=4
Dependent variable
Constant
(The number that depended
on the independent variable)
(It stayed the same)

7. A birdy example…
Imagine you want to see what color of bird feeders your local birds preferred.
Red? Blue? Green?
If a student wanted to determine whether feeder color has an effect, he might suggest, “if I put up a red, blue, and green feeder, birds will visit the green feeder more” as a hypothesis. He might speculate that the green feeder, being the most “camouflaged” or “natural” might be visited the most.

8. Our Experimental Design
Controlled variables
Location of feeders
Kind of seed
Type of feeder
Independent
Variable
Red
Blue
Green
Dependent
Amount of Seed Eaten

9. The experiment is FAIR. (ONLY the independent variable can change!)
If everything except the independent variable is held constant, we can say:
The experiment is FAIR.
(ONLY the independent variable can change!)

10. Is Sam’s experiment fair? YES? NO?
Read the following scenario to the students:
Sam wants to know if birds prefer one color of feeder to another. He makes three feeders out of 2-liter bottles and paints one red, one blue, and one green. He fills the feeders with the same amount of sunflower seed, and plans to keep the feeders out for one week before measuring how much seed is eaten out of each. On Tuesday, he puts each of the feeders in his back yard: the red feeder in a large dead tree, the blue feeder he sits on the doghouse, and the green one he puts in a small bushy tree.
Is Sam’s experiment fair?

11. Why is it important to change only 1 thing at a time?
Collect answers…

12. If you don’t… then you won’t know what is causing your results.
Give an example: a girl wanted to know whether her dog being out in the backyard scared birds away. She thought it would, because the dog likes to bark a lot and has been known to chase little animals.
For 5 days when the dog was out, she counted for an hour.
For 5 days the dog wasn’t out, she counted for an hour.
After she collected the data, she noticed that birds are actually out MORE when the dog is in the yard. Does that surprise you?
But, what the girl didn’t think of was other things that might effect the number of birds that were out. She began thinking that maybe something else might be going on. She realized that the dog was out on sunny warm days, and not on rainy, cool days.
So, even though she found a change, how will she know if it was the dog may have had an effect? Or was it the weather?
See if kids can suggest improvements to the experiment. (i.e. making sure the weather and temperature is similar on the days she counts.)
Independent Variable

13. For Example:

14. 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.

15. Identify the variables in this investigation.

16. What was the independent variable?
Ages of the students
Different ages were tested by the scientist

17. What was the dependent variable?
The time it to put the puzzle together
The time was observed and measured by the scientist

18. What was a controlled variable?
Same puzzle
All of the participants were tested with the same puzzle.
It would not have been a fair test if some had an easy 30 piece puzzle and some had a harder 500 piece puzzle.

19. Another example:

20. 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.

21. What are the variables in this investigation?

22. Independent variable:
Sizes of nails
These were changed by the scientist

23. Number of paper clips picked up
Dependent variable:
Number of paper clips picked up
The number of paper clips observed and counted (measured)

24. Controlled variables:
Battery, wire, type of nail
None of these items were changed

25. One more:

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

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

28. Last one:

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

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?

34. What do you think?
Terry loves birds and wants to see as many as she can in her yard. She wants to know whether she is wasting money buying an expensive mixed seed, when a cheaper brand just arrived at her local store. She wonders… will the expensive seed attract more birds to her back yard?
You may want to have students brainstorm in pairs, or conduct a group discussion.
How would you advise her to find out if the expensive seed is better?

35. Terry’s Experimental Design
Independent
Variable ?
Dependent
Constants
What is the Independent Variable?
What is the Dependent Variable?
What would you hold constant?

36. Terry’s Experimental Design
Independent
Variable
Kind of seed:
Expensive Cheap
Dependent
Number (and perhaps kinds) of birds that visit
Constants
Location of feeders
Type of feeder
Way she measures the amount of seed eaten and the way she counts birds $
What is the Independent Variable?
What is the Dependent Variable? Number of birds– also, you may want to record what KINDS visit. Maybe diversity is higher with one seed or the other!
What would you hold constant? There are other answers as well. Feel free to add to the list

37. Bellringer
A study was done to find if different tire treads affect the braking distance of a car.
Independent Variable:__________________________________
Dependent Variable:___________________________________
Controlled Variable:____________________________________
2. An experiment was performed to determine how the amount of coffee grounds could affect the taste of coffee. The same kind of coffee, the same percolator, the same amount and type of water, the same perking time, and the same electrical source were used.
Independent Variable:___________________________________
Dependent Variable:_____________________________________
Different tire treads
Braking distance
The car
Amount of coffee grounds
Taste of coffee

38. Bellringer 8-15 1 - Patty Power
Mr. Krabbs wants to make Bikini Bottoms a nicer place to live. He has created a new sauce that he thinks will reduce the production of body gas associated with eating crabby patties from the Krusty Krab. He recruits 100 customers with a history of gas problems. He has 50 of them (Group A) eat crabby patties with the new sauce. The other 50 (Group B) eat crabby patties with sauce that looks just like new sauce but is really just mixture of mayonnaise and food coloring. Both groups were told that they were getting the sauce that would reduce gas production. Two hours after eating the crabby patties, 30 customers in group A reported having fewer gas problems and 8 customers in group B reported having fewer gas problems.
1. What is the independent variable?
2. What is the dependent variable?
3. What should Mr. Krabs’ conclusion be?
4. Why do you think 8 people in group B reported feeling better?