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Scientific Method

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					Scientific Method
Steps in the Scientific
        Method
               Observation
               Hypothesis
               Experiment
               Data Collection
               Conclusion
               Retest
   An example of an      Observations
 observation might be
  noticing that many
  salamanders near a
pond have curved, not
  straight, tails. The
 pond is located by a
 farmers field where
     pesticides are
 regularly sprayed on
         crops.
        Hypothesis
   A suggested
    solution to the
    problem.
   Must be testable
   Sometimes written
    as If…Then…
    statements
   Predicts an
    outcome
         Hypothesis
 An example of a
  hypothesis :
If the concentration
of a pesticide is
increased, then there
will be a greater
percentage of
salamanders with
curled tails.
     Experiment!!
A defined and
   specific
  procedure
structured to
   test the
 hypothesis.
Some rules:
   Change one factor (variable) and
    observe or measures what
    happens.
   Control all other factors (referred
    to as ‘controlled variables’)
   Use a control group when possible
   Quantify data as much as
    possible.
   Collect qualitative data as well!
Are the controlled variables the
same thing as the control group?
       No! Explain!
What is the Purpose of a
    control group?
 Control groups are not under
  testing parameters.
 Control groups often

  symbolize the normal state.
 They are often used for
  COMPARISON
          Other Variables
   The factor that is changed is known as the
    independent variable (ex. We change the
    type of additive (pesticide or not) that we
    give to each individual in a test group)
   The factor that is measured or observed is
    called the dependent variable (ex. We
    measure the effects of the pesticide (or
    not) on growth/change in tail of
    salamander)
               Example
   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.
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
     control variable.
One more thing… it is best
to make several trials with
each independent variable.
Data                    Must be organized
   Results of the    Can be organized into
    experiment       charts, tables, or graphs

   May be
    quantitative
    (numbers) or
    qualitative
           Conclusion

   The answer to
    the hypothesis
    based on the
    data obtained
    from the
    experiment
        Retest

In order to
 verify the
   results,
experiments
   must be
  retested.
                 Example:
             Potato Chips and
              Stomach Aches
   Researchers tested the prediction that
    Olestra® in potato chips causes cramps
       Experimental group: Olestra chips
       Control group: regular chips
 Hypothesis
Olestra® causes intestinal cramps.


Prediction
  People who eat potato chips made with Olestra will be
 more likely to get intestinal cramps than those who eat
           potato chips made without Olestra


Experiment       Control Group       Experimental Group
                  Eats regular          Eats Olestra
                  potato chips          potato chips



Results          Control Group       Experimental Group
                  Eats regular          Eats Olestra
                  potato chips          potato chips



Conclusion
   Percentages are about equal. People who eat potato
     chips made with Olestra are just as likely to get
  intestinal cramps as those who eat potato chips made
                     without Olestra.                         Stepped Art
       These results do not support the hypothesis.        Fig. 1-10, p. 14
Sampling Error in Experiments
   Researchers experiment on subsets of a
    group
       Results may differ from results of the same
        experiment performed on the whole group
   Sampling error is a difference between
    results from a subset and results from the
    whole
       Small sample size increases the likelihood of
        sampling error in experiments
Practice makes perfect
   Complete Simpsons Handout NOW
   Complete Scientific Method in Action
    Handout NOW or for homework!

				
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posted:11/27/2011
language:English
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