1. Experimental Design

2. Experimental Investigation The organized procedure used to study an aspect of the natural world under controlled conditions

3. Experimental Design Testable Question Research Hypothesis Materials/Procedure Data Collection Data Analysis Conclusion

4. Testable Questions Asks the question to be answered in an experiment Includes both the independent variable and the dependent variable How does ____(Independent Variable)____ affect ___(Dependent Variable)____? What is the effect of ___(Independent Variable)___ on ___(Dependent Variable)____?

5. Practice Writing a Testable Question Using the following information, write a testable question: Independent variable: hours of studying Dependent variable: grade earned on a test

6. Hypothesis A prediction based on prior knowledge (research) about the expected relationship between the variables in an experiment Includes both the independent variable and the dependent variable and a reason Is either supported or rejected by the experiment Frequently written as an “if…then” statement Example “If the amount of sunlight received by a plant is increased, then the plant will grow taller because plants require sunlight for photosynthesis”

7. Practice Writing a Hypothesis Write a hypothesis for the following question: What is the effect of exercise on a person’s heart rate?

8. Research Before beginning an experiment, quality research must be conducted to gather background knowledge Reliable sources (peer-reviewed journals, textbooks, etc.) *Not wikipedia or blogs* Also included in the background knowledge are previous observations

9. Parts of an Experiment Independent Variable Dependent Variable Controlled Variable

10. Independent Variables Also called manipulated variables Changed (manipulated) directly by the scientist Graphed on the X-axis (horizontal)

11. Dependent Variables Also called responding variables Change as a result of the manipulation of independent variables Graphed on the Y-axis (vertical)

12. Controlled Variables Also called constants Do not change during an experiment Must stay the same in order to ensure a fair test

13. Control Group A standard or “baseline” group to which the experiment is compared The independent variable is not changed in the control group For example, if the scientist is testing how the addition different fertilizers affect a plant’s growth, the control group would be a plant that does not receive any fertilizer

14. Materials List List specifically all materials used in an experiment Include quantities and units For example, “beakers” is not specific. Instead, write “5 100 mL beakers”

15. Procedure A step-by-step guide to conducting an experiment Procedures must be specific and detailed Include all tools and materials being used in that step Procedures should be detailed enough that the experiment can be repeated by another scientist

16. Organizing Data Quanitative (numerical) data is organized into tables or charts in rows and columns Specific independent variables are listed The number of trials are listed Blanks are left to fill in measured data (dependent variable)

17. Title Describing the Data (ex: Independent Variable vs. Dependent Variable) TrialIndependent Variable 1 Independent Variable 2 Independent Variable 3 1 2 3 4 Average

18. Analyzing Data Reduce the data: do something to make the amount of data smaller Central tendencies: Mean Median Mode Range Frequency

19. Bar Graphs Uses rectangular bars of different colors/patterns to display data Used for comparisons

20. Line Graphs Uses points connected by a line to show how values change Useful for showing trends

21. Scatter Plots Uses unconnected points to display data Useful for showing correlations between variables Note: correlation does not imply causation! A correlation between variables does not necessarily mean that one immediately caused the other to change

22. Positive Correlation An increase in the variable on the X-axis is associated with an increase in the variable on the Y-axis

23. Negative Correlation An increase in the variable on the X-axis is associated with an decrease in the variable on the Y-axis

24. No Correlation Random data points – there is no association between the variables

25. DRY MIX Dependent Responding Y-Axis Manipulated Independent X-axis

26. Let’s Practice Title Independent Variable Dependent Variable X Y

27. *Don’t Forget* Every time you make a graph, include: Descriptive title (ex: Independent Variable vs. Dependent Variable) Labeled X and Y axes… Include UNITS Legend (if necessary) Scale/Interval of axes (3, 6, 9, etc)

28. Let’s Practice Time (minutes) Cart 1 Distance (m) Cart 2 Distance (m) Cart 3 Distance (m) 1123 2246 3369 44812 A student built three different wooden carts to test the effect of different power sources (battery, wind, and solar) on the speed of her carts. Her data is represented in the table above.

29. Conclusion Answers the original question Restate the hypothesis Accept or reject the hypothesis and support using evidence from the investigation Describe relationships in the data Explain any inferences made using the data Discuss any problems or sources of error that occurred during the investigation Discuss any extensions or elaborations on the topic

30. Publish! New knowledge is useful when it is shared Journals, publications, presentations