1. EXPERIMENTAL DESIGN
Science answers questions with experiments

2. Begin by asking a question about your topic
DEFINE THE PROBLEM
Begin by asking a question about your topic
What is a good question for an experiment?
One that is testable with the materials at hand

3. Now we need a hypothesis to guide our investigation.
What is a hypothesis?
No, It is NOT an educated guess!
Your best thinking about how the change you make might affect another factor Tentative or trial solution to the question. An if ………… then ………… statement.

4. Variables Variables are things that change.
The independent variable is the variable that is purposely changed. It is the manipulated variable.
The dependent variable changes in response to the independent variable. It is the responding variable.
Be sure to operationally define each variable.

5. Factors that are kept the same and not allowed to change
Constants in an Experiment
What are constants in an experiment?
Factors that are kept the same and not allowed to change

6. The part of the experiment that serves as the standard of comparison.
The Control in an Experiment
What is a control?
The part of the experiment that serves as the standard of comparison.
Why is a control necessary?
It is the unchanged part of the experiment that detects the effects of hidden variables.

7. Materials and Procedures
A description of what you will use for your experiment, and how you will do it.
Be sure to include:
Levels of the Independent Variable
Repeated Trials
Drawing of Apparatus

8. Levels of the Independent Variable
How many different levels of the independent variable should we test?
3 ? ? ? The more the better?

9. Repeated Trials What are repeated trials?
The number of times that a level of the independent variable is tested.
Why are repeated trials necessary?
They reduce the possibility of chance errors affecting the results.

10. Drawing of Experiment
Include Labels to clearly identify the important parts of the experimental setup

11. Qualitative Observations and Results
What are qualitative observations?
They are what you perceive that occurred during the course of your experiment. They are identification of trends in the data.

12. Quantitative Observations and Results
What are quantitative observations?
Numbers in the form of raw data displayed in data tables and graphs

13. Sample Data Table
Title: The Effect of the independent variable on the dependent variable
Column for independent variable
Column for dependent variable
Column for derived quantity
Label – with units if necessary
Label – with units if necessary – multiple trials included
Label – with units if necessary. Example = average of trials 1 4 2 6 3 7 9

14. What’s wrong with this table? 14 17 8 10 6 7 4 2
Average temp. change (oC)
Temp. Change of water (oC) Trials
Number scoops of calcium chloride

15. What’s wrong with this table?
The Effect of Various Amounts of Calcium Chloride on the Temperature of Water 14 17 8 10 6 7 4 2
Average temp. change
Temp. Change of water Trials
Number scoops of calcium chloride

16. What’s wrong with this table?
The Effect of Various Amounts of Calcium Chloride on the Temperature of Water 14 17 8 10 6 7 4 2
Average temp. change (oC)
Trials
Number scoops of calcium chloride

17. What is the purpose of a graph?
Constructing a Graph
What is the purpose of a graph?
Graphs communicate in pictorial form the data collected in an experiment

18. Independent Variable – include units and an appropriate scale
Graphs
Title: The Effect of the independent variable on the dependent variable
Dependent Variable – include units and an appropriate scale
Independent Variable – include units and an appropriate scale

19. The type of graph to use depends on the type of data collected.
Bar vs. Line Graphs - Which Should I Use?
The type of graph to use depends on the type of data collected.
Two kinds of data: Discrete and Continuous
Discrete data are categorical like days of the week, color, and brand of battery. Intervals between the data have no meaning.
USE A BAR GRAPH
Continuous data are associated with measurements
involving a standard scale. Measurements should be able to show a trend or relationship. Intervals between data have meaning.
USE A LINE GRAPH

20. Constructing a Graph DRAW AND LABEL AXES
Y Axis - Dependent Variable
Temp. of Water (oC)
Amount of Calcium Chloride (scoops)
X Axis - Independent Variable

21. Constructing a Line Graph - DETERMINE SCALES FOR AXES
Increase values on axes by 1, 2 ,5, 10 or
multiples of 10. There should be about
5 numbered subdivisions on each axis. 20 15
X: Largest value – Smallest value = Range
10 scoops - 0 scoops = 10 scoops
10 scoops divided by 5 = 2 scoops 10
Average Temp. change (o C)
Y: Largest value – Smallest value = Range oC – 0 oC = 17 oC o C divided by 5 = 3.4 or ~ 5 oC 5
Amount of calcium chloride (scoops)

22. . . . . . . Constructing a Line Graph – PLOT DATA PAIRS 20
(0, 0)
(2, 4)
(4, 7)
(6, 10)
(8, 14)
(10, 17) . 15 .
Average Temp. change (deg C) 10 . . 5 .
Amount of calcium chloride (scoops)

23. . . . . . . Constructing a Line Graph – DRAW A LINE-OF-BEST-FIT 2015 .
Average Temp. change (deg C) 10 . . 5 .
Amount of calcium chloride (scoops)

24. . . . . . . Constructing a Line Graph – TITLE THE GRAPH 20 15
THE EFFECT OF ADDING VARIOUS AMOUNTS OF CALCIUM CHLORIDE ON THE TEMPERATURE OF WATER . 20 . 15 .
The title should state the effect of the independent variable on the dependent variable. 10 .
Average Temp. change (oC) . 5 .
Amount of calcium chloride (scoops)

25. TEST YOUR UNDERSTANDING Q1- What is wrong with this graph?
THE EFFECT OF ADDING VARIOUS AMOUNTS OF CALCIUM CHLORIDE ON THE TEMPERATURE OF WATER . 20 . 15 . 10 .
Average Temp. change (oC) . 5 . 1 3 5 7 9
Amount of calcium chloride (scoops)

26. TEST YOUR UNDERSTANDING Q2 - What is wrong with this graph?
THE EFFECT OF ADDING VARIOUS AMOUNTS OF CALCIUM CHLORIDE ON THE TEMPERATURE OF WATER . 17 . . 14 10 .
Average Temp. change (oC) . 7 4 .
Amount of calcium chloride (scoops)

27. TEST YOUR UNDERSTANDING Q3 - What is wrong with this graph?
THE EFFECT OF ADDING VARIOUS AMOUNTS OF CALCIUM CHLORIDE ON THE TEMPERATURE OF WATER . 20 . 15 .
Average Temp. change 10 . . 5 .
Amount of calcium chloride

28. TEST YOUR UNDERSTANDING Q4 - What is wrong with this graph?.
THE EFFECT OF ADDING VARIOUS AMOUNTS OF CALCIUM CHLORIDE ON THE TEMPERATURE OF WATER 10 . 8 .
Amount of Calcium Chloride (scoops) 6 . 4 . . 2
Average Temp. Change (oC)

29. TEST YOUR UNDERSTANDING Q5 - What is wrong with this graph?
THE EFFECT OF ADDING VARIOUS AMOUNTS OF CALCIUM CHLORIDE ON THE TEMPERATURE OF WATER . 20 . 15 . 10 .
Average Temp. change (oC) . 5 .
Amount of calcium chloride (scoops)

30. TEST YOUR UNDERSTANDING Q6 - What is wrong with this graph?. 20 . 15 . 10 .
Average Temp. change (oC) . 5 .
Amount of calcium chloride (scoops)

31. . . . . . . TEST YOUR UNDERSTANDING
Q7 - What is wrong with this graph?
THE EFFECT OF ADDING VARIOUS AMOUNTS OF CALCIUM CHLORIDE ON THE TEMPERATURE OF WATER 40 30 . . 20
Average Temp. change (oC) . . . 10 .
Amount of calcium chloride (scoops)

32. Analysis and Interpretation of Results
This is where you describe in words what is illustrated by your data as shown in your table and graph You also describe the meaning of the results

33. Possible Experimental Errors
What factors in your materials or procedure might have had an impact on your results?

34. Include reasons for the hypothesis to be supported or unsupported.
Conclusion
Why or why not your results supported or did not support the hypothesis.
Hypotheses are never “wrong”. They are either supported or not supported.
Include reasons for the hypothesis to be supported or unsupported.

35. Recommendations for Further Experimentation
What are some practical applications of your results?
What other questions that could be tested arise from your results?

36. Writing A Statement of the Problem for the Experiment
What should it state?
It should state: “The Effect of the Independent Variable on the Dependent Variable”.
What is a good statement of the problem for “The Helicopter?
What is the effect of wing length on time of descent?

37. More about our variables:
The independent variable is the variable that is purposely changed. It is the manipulated variable.
The dependent variable changes in response to the independent variable. It is the responding variable.
What is the “Helicopter” independent variable?
length of one wing as measured in centimeters
What is the dependent variable?
time of descent as measured in seconds

38. Title for the Helicopter Experiment
The Effect of Wing Length on the Length of Time the Helicopter Takes to Reach the Ground

39. Another Look at Our Hypothesis
INDEPENDENT VARIABLE
If the length of the wings are increased,
DEPENDENT VARIABLE
then time of descent will increase.

40. Constants in an Experiment
Factors that are kept the same and not allowed to change
What should be kept constant in the“Helicopter”?
CONSTANTS
Same structure of helicopters
Same dropping technique
Same dropping height

41. The Control in an Experiment
The part of the experiment that serves as the standard of comparison.
What is a good control for the “Helicopter”?
CONTROL
Beginning length of wings (5 cm)

42. Levels of the Independent Variable
How many different levels of the independent variable should we test?
Enough to clearly illustrate a trend in the data - 5cm, 6cm, 7cm, 8cm…..

43. How many repeated trials are needed in the “Helicopter”?
At least 3, then calculate an average value for each level of the independent variable

44. Drawing of Experiment Hold helicopter in the middle
Drop from same spot each time

45. Qualitative Observations and Results
As we dropped the helicopter, we observed that sometimes they seemed to be affected by air currents.
It appeared that helicopters with longer wingspans took a greater time to reach the ground

46. Quantitative Observations
Data Table and Graph

47. Sample Data Table
Title: The Effect of wing length on the time of descent
Descent Time (s)
Trials
Wing Length
(cm)
Average Descent Time (s) 5 6 7 8 9

48. . . . . . The Effect of Wing Length on Descent Time 8 76
Average Descent Time (sec) . 5 . 4
Wing Length (cm)

49. . . . . . The Effect of Wing Length on Descent Time 8 64
Average Descent Time (sec) 2
Wing Length (cm)

50. Analysis and Interpretation of Results
While individual trial results showed some variation; overall, as average wing length increased from 5 through 9 centimeters, average time of descent also increased from 4 through 8 seconds.
This shows a direct correlation.

51. Possible Experimental Errors
Although the average results supported the hypothesis, the individual trial results showed some variation. Some possible reasons for this could be due to air currents in the room or reaction time differences between the timer and the helicopter dropper.

52. Conclusion The overall results supported the hypothesis.
A possible reason for this could be due to increased surface area of the wing in contact with the air - allowing for greater air support.

53. Recommendations for Further Experimentation/ Practical Applications
Increased time of descent due to greater wing length suggests that increased wing length could lead to greater fuel efficiency of an actual helicopter.
Other experiments investigating factors that would contribute to greater descent time might include: making modifications in the shape of the wings, changing the number of wing blades, and making folds in the wing blades

54. Authors
Harry Dillner, Kathy Melvin
Delaware Science Olympiad