Transcript Scientific Method

Experimental Design
Chapter 1
1 Define the Problem
What is it you want to find out?
 Sometimes called the Purpose or
Question
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What are some problems scientists work
on today?
2 Research
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Gather as much information as possible
before experimenting
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Sometimes called collecting information
3 Form a Hypothesis
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Predict the outcome of your
experimentation
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Sometimes called an educated guess
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Many times hypotheses are stated in the
“If…… then…..” format
4 Experiment
Develop a procedure to test the
hypothesis.
 Change only one variable at a time and all
other things as constants.
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Independent variable – the thing you
change.
 Sometimes called test the hypothesis
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5 Analyze the Data
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Record the results of your experiment
using charts, graphs, and taking notes
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Sometimes called analysis or conclusions
6 Conclusion
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Compare the hypothesis to the
experiment’s conclusion and publish your
results for others to see
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Sometimes called communicate the
results
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Paul Revere Hates Eggs And Cheese
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The Strange Case of BeriBeri
In 1887 a strange nerve disease attacked the people in the Dutch
East Indies. The disease was beriberi. Symptoms of the disease
included weakness and loss of appetite, victims often died of
heart failure. Scientists thought the disease might be caused by
bacteria. They injected chickens with bacteria from the blood of
patients with beriberi. The injected chickens became sick.
However, so did a group of chickens that were not injected with
bacteria.
One of the scientists, Dr. Eijkman, noticed something. Before the
experiment, all the chickens had eaten whole-grain rice, but
during the experiment, the chickens were fed polished rice. Dr.
Eijkman researched this interesting case. he found that polished
rice lacked thiamine, a vitamin necessary for good health.
1. State the Problem
2. What was the hypothesis?
3. How was the hypothesis tested?
4. Should the hypothesis be supported or rejected based on the
experiment?
5. What should be the new hypothesis?
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How Penicillin Was Discovered
In 1928, Sir Alexander Fleming was studying Staphylococcus
bacteria growing in culture dishes. He noticed that a mold called
Penicillium was also growing in some of the dishes. A clear area
existed around the mold because all the bacteria that had grown in
this area had died. In the culture dishes without the mold, no clear
areas were present.
Fleming hypothesized that the mold must be producing a chemical
that killed the bacteria. He decided to isolate this substance and test
it to see if it would kill bacteria. Fleming transferred the mold to a
nutrient broth solution. This solution contained all the materials the
mold needed to grow. After the mold grew, he removed it from the
nutruient broth. Fleming then added the nutrient broth in which the
mold had grown to a culture of bacteria. He observed that the
bacteria died.
6. Identify the problem.
7. What was Fleming's hypothesis?
8. How was the hypothesis tested?
9. Should the hypothesis be supported or rejected based on the
experiment?
10. This experiment led to the development of what major medical
advancement?
When Experiments are Testing for
something they have …..
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Independent variable (I.V.)- the factor (or
variable) that gets changed on purpose in
an experiment while all others remain
constant.
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I.V. – I changed it myself
Dependent Variable
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The factors (or variables) that get changed
as a result of the independent variable in
an experiment
The thing you measure
 It depends or changes because of the I.V.
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Constants
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The factors in an experiment that remain
the same. They are not changed.
Control
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The group that has no variable acting
upon it so that it can be compared with the
results of the experiment
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In drug tests, this group is given sugar pills
(placebos) instead of the medicine. They
are told it is medicine.
Types of Data
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Quantitative – has numbers, obtained by
counting, measuring.
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Qualitative – descriptions that do not use
numbers, including colors, tastes, smells,
sound or textures
Qualitative or Quantitative
The floor is shiny.
 There are 19 students in the class.
 The walls are white.
 The board is 1 meter high and 2 meters
wide.
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