# 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

   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 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

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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 views: 1 posted: 11/27/2011 language: English pages: 20