Scientific Method

1. Scientific Method

2. Steps in the Scientific Method • Observation • Hypothesis • Experiment • Data Collection • Conclusion • Retest

3. Observations • Gathered through your senses • A scientist notices something in their natural world

4. Observations • An example of an observation might be noticing that many salamanders near a pond have curved, not straight, tails

5. Hypothesis • A suggested solution to the problem. • Must be testable • Written as If…Then… statements • Predicts an outcome

6. Hypothesis • An example of a hypothesis might be that if there is pollution in the soil, then a salamander will have a curved tail.

7. Experiment • A procedure to test the hypothesis. • Can be an experiment, model, or observation

8. Parts of an Experiment Variable – factor in the experiment that is being tested

9. Experiment A good or “valid” experiment will be repeatable and change only one variable at a time

10. Experiment • A good experiment will also have many replicates (individuals) • n=sample size

11. Experiment

12. Controls,Variables, and Constants

13. Scientific Experiments Follow Rules • An experimenter changes one factor and observes or measures what happens.

14. Constants • The experimenter makes a special effort to keep other factors constant so that they will not effect the outcome.

15. Controls • Controls establish a “status quo” • That’s how conditions are under normal circumstances.

16. What is the Purpose of a Control? • Controls are NOT being tested • Controls are used for COMPARISON

17. Independent Variable • The factor that is changed by the experimenter is known as the independent variable. • Its effects are measured by changes in the dependent variable • It will be graphed on the X-AXIS

18. Dependent Variable • The factor that is measured or observed is called the dependent variable. • Observed and measured during the experiment • Graphed on the Y-AXIS

19. Graphing Variables

20. Example of Controls,Variables, and Constants • For example, suppose you want to figure out the fastest route to walk home from school. • You will try several different routes and time how long it takes you to get home by each one. • Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.

21. What are the Variables in Your Experiment? • Varying the route is the independent variable • The time it takes is the dependent variable • Keeping the same walker throughout makes the walker a constant. • There is NO CONTROL.

22. One more thing… it is best to make several trials with each independent variable.

23. Valid Experiments

24. Remember: To be a Valid Experiment: • Two groups are required --- the control & experimental groups • There should be only one variable each experiment

25. Data • Results of the experiment • May be quantitative (numbers) or qualitative (descriptive)

26. Data • Must be organized • Can be organized into charts, tables, or graphs

27. What are trends in graphs? • Negative (inverse) • When one increases, the other decreases • Positive (direct) • When one increases, the other increases OR when one decreases, the other decreases • No relationship • One has NO EFFECT on the other.

28. Conclusion • The answer to the hypothesis based on the data obtained from the experiment

29. Why do scientists repeat experiments? • In order to verify results, experiments must be RETESTED! • It adds validity to the findings.

30. How do scientists communicate findings? • When scientists want to communicate the results of their experiment, they use SCIENTIFIC JOURNALS or other publications!

31. What is pure and applied science? • Pure Science • Answers questions about phenomena and mechanisms in the natural world. • Why do you do it? • Because we wanted to know! • EX. Studying the ICE MAN • Applied Science • Application of scientific knowledge to practical problems. • Why do you do it? • To fight disease, identify criminals, learn how to store hazardous wastes…etc.

32. What are the variables of an experiment? • Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, they're supposed to staple a set of papers). Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks. • Independent Variable • Special juice • Dependent Variable • How many stacks are made • Control • No special juice given (normal group) • Constant • 50 workers in each group.

33. What is an experimental control? • Lisa is working on a science project. Her task is to answer the question: "Does Rogooti (which is a commercial hair product) affect the speed of hair growth". Her family is willing to volunteer for the experiment. • Set up an experiment to test this. • What would the independent variable be? • Whether a family member gets Rogooti or not. • What would the dependent variable be? • Hair growth • What would the control be? • The family members that do NOT get Rogooti • Is there a constant? • No.

34. The conclusion • Lisa is working on a science project. Her task is to answer the question: "Does Rogooti (which is a commercial hair product) affect the speed of hair growth". Her family is willing to volunteer for the experiment. • Marge and Homer used Rogooti and grew 14 inches of hair in two weeks. An inch a day. • Maggie and Bart did NOT use Rogooti and grew 2 cm of hair in two weeks. • What should Lisa conclude? • How would she represent this information?

35. Review