Scientific Method

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Scientific Method
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Steps in the Scientific Method

• Observation
• Hypothesis
• Experiment
• Data Collection
• Conclusion
• Retest

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Observations

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

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Observations

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

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Hypothesis

• A suggested solution to the problem.
• Must be testable
• Written as IfThen statements
• Predicts an outcome

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Hypothesis

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

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Experiment

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

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Parts of an Experiment
Variable factor in the experiment that is
being tested
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Experiment
A good or valid experiment will be repeatable
and change only one variable at a time
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Experiment

• A good experiment will also have many replicates
  (individuals)
• nsample size

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Experiment
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Controls,Variables, and Constants
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Scientific Experiments Follow Rules

• An experimenter changes one factor and observes
  or measures what happens.

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Constants

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

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Controls

• Controls establish a status quo
• Thats how conditions are under normal
  circumstances.

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What is the Purpose of a Control?

• Controls are NOT being tested
• Controls are used for COMPARISON

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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

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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

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Graphing Variables
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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.

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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.

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One more thing it is best to make several trials
with each independent variable.
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Valid Experiments
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Remember To be a Valid Experiment

• Two groups are required --- the control
  experimental groups
• There should be only one variable each experiment

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Data

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

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Data

• Must be organized
• Can be organized into charts, tables, or graphs

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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.

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Conclusion

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

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Why do scientists repeat experiments?

• In order to verify results, experiments must be
  RETESTED!
• It adds validity to the findings.

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How do scientists communicate findings?

• When scientists want to communicate the results
  of their experiment, they use SCIENTIFIC JOURNALS
  or other publications!

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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 wastesetc.

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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.

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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.

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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?

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Review