1. How do scientists perform GOOD experiments?
THE SCIENTIFIC METHOD
How do scientists perform GOOD experiments?

2. The Scientific Method
A universal approach to scientific problem solving through a series of well-defined steps

3. The Steps of the Scientific Method
Question/Problem (?) do Research
Hypothesis (I think that…)
Experiment/Procedure
Perform a GOOD experiment!
Results/Data (Include a table and graph)
Conclusion
Was your hypothesis right or wrong? Analyze the data.

4. PROBLEM 1- Defining the Problem -Stated in the form of a question that
defines a specific problem for
investigation
Ex- Do plants need water to grow?

5. RESEARCH 2- Research the Problem - Library, internet, periodicals,
textbooks, encyclopedias, newspaper,
scientists, teachers, TV

6. HYPOTHESIS 3- Develop a Hypothesis (educated guess)
- A possible explanation for an observed
set of facts
- Reasoning, guesswork, and inspiration
Ex- Plants need water to grow

7. PROCEDURE 4- Procedure (Design an experiment to test the hypothesis)
- list of materials
- detailed and easy to follow step by step
set of instructions for carrying out
experiment.

8. Tips for Designing Good Experiments
BE SPECIFIC!!!
Always have a control group. (Something to compare your results to.)
Keep all the conditions constant except one (Variable).
Experiment on LOTS of subjects.
Test the experiment more than once.
Be objective (unbiased).

9. What is the control group for?
The purpose of the CONTROL group is to have something to COMPARE your experimental results to.

10. reference setup, standard for comparison
Constants- Factors that are not changed (Ex- plants, soil, sunlight, location)
Control- No factors are changed, a
reference setup, standard for comparison

11. PROCEDURE Variable- A factor that changes in an experiment
Independent variable- factor which is changed as part of the procedure (what is being tested) Ex- amount of water for plants
Dependent variable- factor that changes as a result of the independent variable.
(example: plant growth (data)

12. Your 2 groups of test subjects:
Control Group= Normal Group, gets nothing.
Experimental /independent group Gets the Ind. Variable
The 2 things that are allowed to be different:
Independent Variable = What you varied on purpose.
Dependent Variable = What varied as a result of your experiment.
Constants: Things that can NOT vary.

13. Practice: Which is the CONTROL GROUP?
Hypothesis:
Hand Soap will work to kill bacteria.
Procedure:
I wash my hands with water only.
I wash my hands with soap and water.

14. Practice: Which is the CONTROL GROUP?
Hypothesis:
Students will stay more alert during school if they eat a high protein breakfast.
Procedure:
Students eat a regular cereal breakfast.
Students eat a high protein breakfast.

15. Practice: Fertilizer Growth Independent Dependent
I changed the amount of fertilizer the plants got to see if they would grow more quickly with fertilizer.
Independent
Dependent
Fertilizer
Growth

16. I changed the amount of Tylenol people got to see if their headache would go away.
Independent
Dependent
Tylenol
Relief

17. Light/darkness Green color
Bill put some of his plants in the dark to see if they would stay green.
Independent
Dependent
Light/darkness
Green color

18. Ears covered Come home or not
I covered Homing Pigeons’ ears to see if they could still find their way home.
Independent
Dependent
Ears covered
Come home or not

19. Test/experiment 5- Test the Hypothesis
- experiment and results must be repeatable to be valid
Ex- Plants that are not watered do not
grow

20. DATA 6- Record and Organize Data
Observations – What happened during experiment.
Qualitative Observations- descriptions based on observer’s senses (Ex- Watered plants are taller)
Quantitative Observations- accurate measurements and numerical results obtained using tools and instruments (Ex- The watered plants grew 3 inches more than those that were not watered)

21. DATA Record Data- Charts, graphs, Tables, Diagrams, Photographs
Analyze Data- Look for patterns or
relationships
Interpret- try to make sense of the data

22. CONCLUSIONS 7- Interpret results and draw conclusions
Does data support, modify or disprove hypothesis?
The conclusion is the answer to the original problem and should prove or disprove the hypothesis.
Ex- Plants need water to grow

23. What if your hypothesis is wrong?
I think fertilizer will help plants grow taller.
That’s great! You proved something!

24. If your experiment is valid…
…then other people should be able to repeat it and get the SAME results.

25. REPORT
All aspects of an experiment must be recorded accurately and reported in detail so that it can be repeated by other investigators
If good enough then it is published in scientific journals.

26. THEORIES
Explanations that apply to a broad range of phenomena and are supported by experimental evidence, attempts to explain the cause of the phenomena
Ex- The Theory of Evolution

27. SCIENTIFIC LAW
Describe an aspect of a phenomena that is always true, a particular event or relationship always exists under certain conditions
Does not explain how or why
Ex- Law of Gravity

28. Practice problems Which Step is It?

29. that seeds would start to grow faster
Stephen thought
that seeds would start to grow faster
if an electric current traveled through the soil in which they were planted.
Question
Hypothesis
Experiment
Results
Conclusion

30. Jonathan’s data showed that household cockroaches moved away from raw cucumber slices.
Question
Hypothesis
Experiment
Results
Conclusion

31. Rene grew bacteria from the mouth on special plates in the laboratory.
She placed drops of different mouthwashes on bacteria on each plate.
Question
Hypothesis
Experiment
Results
Conclusion

32. Kevin said, “If I grow five seedlings in red light, I think the plants will grow faster than the five plants grown in white light.”
Question
Hypothesis
Experiment
Results
Conclusion

33. Angela’s experiment showed that earthworms moved away from light
Angela’s experiment showed that earthworms moved away from light. She thinks this may be because it helps them dig deeper in the ground.
Question
Hypothesis
Experiment
Results
Conclusion

34. Kim’s experiment showed that chicken egg shells were stronger when she gave the hens food with extra calcium.
Question
Hypothesis
Experiment
Results
Conclusion

35. Practice experiments
Do plants grow better with fertilizer?

36. Control Group=
Does not get the variable.
Experimental Group= Receives the variable
Constants= The factors that must remain constant between the two groups.

37. Which factors should remain constant?
Sunlight
Water
Type of plant
Age of plant
Size of plant
Throw out your work and start over!
What if you don’t keep these the same?

38. YOU CAN ONLY CHANGE ONE FACTOR.
Fertilizer

39. Hypothesis: I think fertilizer will help bean plants grow taller.
Procedure:
You take a bean plant and give it 4 scoops of fertilizer per day.
You watch it grow for 3 weeks.
No Control Group

40. Procedure: You use 2 plants.
One has no fertilizer, one has 4 scoops per day.

41. What can we fix about this experiment?
Use more plants!!

42. Practice experiments
Tylenol experiment

43. Tylenol Experiment No Control Group
Hypothesis:
I think Tylenol will get rid of a headache.
Procedure:
Find 50 people with headaches.
Give them each 2 Tylenol.
See if they feel better in 20 minutes.
No Control Group

44. Tylenol Experiment I think Tylenol will get rid of a headache.
Hypothesis:
I think Tylenol will get rid of a headache.
Procedure:
Find 100 people with headaches.
Give 50 of them 2 Tylenol.
Give 50 of them NOTHING.
See if they feel better in 20 minutes.

45. Results
50 got Tylenol
40 felt better
50 got nothing
10 felt better

46. What about the Placebo Effect?
Sometimes people imagine that they feel better just because they took something.
How should we change our experiment to see if the placebo effect is taking place?
Ahhhhh!
Much better!

47. Tylenol Experiment Find 100 people with headaches.
Procedure:
Find 100 people with headaches.
Give 50 of them 2 Tylenol.
Give 50 of them a Placebo (2 sugar pills).
See if they feel better in 20 minutes.

48. Placebo = Control
The placebo group is a type of control group.

49. Results
50 got Tylenol
41 felt better
50 got Placebo
33 felt better

50. Practice experiments
Will mice who receive coca cola run faster on the wheel?

51. Question:
Will mice who receive Coke run faster on the wheel?

52. Experimental Group of Mice
Control Group of Mice
Experimental Group of Mice
100 mice
100 mice
Constants:
Same type of mice
Same size of cage
Same gender
Same food
Same temperature
Same time of day

53. Experimental Group of Mice
Control Group of Mice
Experimental Group of Mice
100 mice
100 mice
Independent Variable
Dependent Variable
Coke
IF ______________THEN _____________
Faster running

55. Practice ?
I think
Joan wonders if 30 minutes of exercise a day will help students do better on a math test.

56. ?
Practice
I think
Sara thinks that inchworms will be repelled by the smell of roses.

57. ?
Practice
I think
Karina wonders if Prozac causes weight gain.

59. Contest: Design the best experiment!
Winning group will get:
10/10 on the assignment.
And Homework Passes!
“Non-winning” group will get an appropriate grade out of 10.

60. Design the Best Experiment!
Question 1: Does brushing your teeth 3x a day dramatically affect the whiteness of your teeth as opposed to 2x a day?
Group 2: Does cigarette smoke affect the growth (size) of an embryo?
Question 3: Does the colorfulness of a peacock’s tail affect his likeliness to attract a mate (peahen)?

61. Remember: Control Group vs Experimental Group Constants
Test a large number of subjects
Ethics (no human subjects can be harmed by your actions)

62. Hand in 1 Neat Copy: Our full names=____________________
Question (SPECIFIC)=
Hypothesis (SPECIFIC)=
The one variable you are changing=
The one factor you are measuring=
Constants=
Procedure (VERY SPECIFIC)
Groups you will have.
What you will do to them.
What data you will collect and how.
Our hypothesis will be correct if____________ (describe the data you would have to get)