The Scientific Method Is the Basis for Scientific Inquiry

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The Scientific Method Is the Basis for Scientific
Inquiry

• Observation of a phenomenon
• Subsequent development of questions
• Formulation of a hypothesis
• A supposition that explains an observed
  phenomenon, leading to testable predictions
• Testing through experimentation
• Additional controlled observations
• Development of a conclusion
• Evaluation of hypothesis in light of experimental
  data

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• Initially, scientists make an observation that
  leads them to a question they want to answer
• This question is turned into a hypothesis or a
  tentative answer to the question
• The hypothesis must be testable and falsifiable

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Controls and Variables in Experimental Design

• Variable are the factors influencing processes
  being examined.
• hypothesis examines ONE variable, holding others
  constant. This is the experimental group.
• Control group examined variable is left
  unaltered

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Applying the Scientific Method to an Everyday
Situation

• You wake up late, miss the bus and your dad has
  to drive you to school, butthe car wont start
• Observation The car wont start
• Hypothesis the battery is dead
• Experimental design Replace your battery with
  another and restart the car
• What conclusion can you draw?

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Limitations of the Scientific Method

• Can never be sure all untested variables are
  controlled
• Conclusions based on the experimental data must
  remain tentative
• Results of experimentation must be communicated
  thoroughly and accurately to other scientists for
  repetition
• Repetition by other scientists add verification
  that findings can be used as the basis for
  further studies

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Science is a Human Endeavor

• Human personality traits are part of real
  science
• Scientists, like other people may be driven by
  pride, ambition, or fear
• Scientists sometimes make mistakes
• Accidents, lucky guesses, intellectual powers,
  and controversies with others contribute strongly
  to scientific advances

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Flemings Discovery of Penicillin Highlights Real
Science in the 1920s

• Microbiologists grow microbes in in pure
  (single-species) cultures on Petri plates
• One of Alexander Flemings bacterial cultures was
  contaminated with a mold
• Fleming nearly destroyed the culture when he
  noticed the mold (Penicillium) inhibited
  bacterial growth on the dish

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• Fleming hypothesized that the mold produced an
  antibacterial substance
• Further tests using broth from pure Penicillium
  cultures lead to the discovery of the first
  antibiotic, penicillin
• Fleming continued beyond a lucky accident with
  further scientific investigation to a great
  discovery
• Chance favors the prepared mind (Louis Pasteur)

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Colds, Vitamins and Nutritional Supplements
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The Logic of Hypothesis TestingInductive vs
Deductive Reasoning

• Hypothesis Consuming vitamin C decreases the
  risk of catching a cold
• This hypothesis is based on observations and
  inductive reasoning A logical process that
  argues from specific instances to a general
  conclusion

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• Prediction If vitamin C decreases the risk of
  catching a cold, then people who take vitamin C
  supplements with their regular diets will
  experience fewer colds than people who do not
  take supplements
• Making predictions about the outcome of a test
  sometimes in if then statements is deductive
  reasoning

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Proof ??? Theory ???

• Even though we cant prove a hypothesis 100
  true, we can gather enough evidence to determine
  whether a hypothesis is reasonably true

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Some Scientific Background

• Experimentation has led to the understanding that
  colds are caused by viruses
• Viruses are composed of
• A small amount of genetic material
• Some proteins
• An outer protective coating

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• Viruses are non-living
• Viruses need to enter a cell to reproduce
• Viruses enter a cell and use the cell machinery
  to make more virus particles, which leave to
  infect more cells
• There are several hundred types of cold viruses
• They normally infect the cells of our noses and
  throats, causing the typical cold symptoms of
  sneezing, coughing, sore throat, and congestion

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Scientific Theory

• Viruses cause the common cold
• Scientists feel this statement is true because
• There are no other reasonable supported
  hypotheses
• This hypothesis has not been rejected
• It conforms to a well-accepted scientific
  principle, the germ theory

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• A scientific theory is an explanation of a set of
  related observations based on well-supported
  hypotheses from several different, independent
  lines of research
• The germ theory arose from the accumulated
  observations of scientists such as Pasteur and
  Koch

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• Scientists in the 1800s noticed a relationship
  between disease and specific microorganisms
• Many experiments and observations since then all
  support the idea that certain microorganisms
  cause human diseases
• Because of the germ theory of disease, science
  believes that colds are caused by viruses, which
  are microorganisms

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A Scientific Theory is not a guess

• Truth in science can be defined as What we
  know and understand based on all available
  information
• If a hypothesis appears to explain all instances
  of a particular phenomenon and has been
  repeatedly tested and supported, it may
  eventually be accepted as accurate
• If there is an abundance of evidence, then the
  idea may be referred to as a theory

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• In common speech, a theory is the same as a
  hypothesis an untested idea
• Is this characteristic of science?
• Is a guess an uncompleted experiment?
• Is one completed experiment enough to form a
  scientific theory?

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Proof??? Theory????

• Many people believe that colds can be treated
  with Echinacea to lessen the duration and
  severity of the cold symptoms

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Experimental Design

• One group drank tea which contained Echinacea
  extract
• A second group (the control group) drank tea
  which did not contain Echinacea extract
• The participants were asked to rate the
  effectiveness of the tea at reducing the cold
  symptoms

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Results

• In this study, people who received echinacea tea
  felt that it was 33 more effective at reducing
  symptoms
• The 33 more effective is in comparison to the
  opinions of people about the effectiveness of a
  tea that did not contain Echinacea extract that
  is, the results from the control group

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What does this really mean?

• Since the only difference between the two groups
  was that the experimental group had Echinacea
  extract in their tea, that difference should
  account for the difference in results
• But was that the only difference?

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Other possibilities

• Were the participants all the same in
• age?
• diet?
• stress level?
• how often they visited a health care provider?
• Do these other variables matter?

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Controls, Controls, Controls

• The only way to be sure that the experimental
  treatment causes the result is to have no other
  differences between the groups
• If this is true, then you have a good robust
  controlled experiment
• Good controls are the basis of strong inference
  a strong statement about the truth of a given
  hypothesis possible when an experimental protocol
  greatly minimizes the number of alternative
  hypotheses that can explain a result

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• In the study, the data indicated that cold
  severity was lower in the experimental group
  compared to the placebo group
• The use of controls in the study allows
  researchers to have high confidence that they
  differed because Echinacea extract relieves cold
  symptoms
• A strong inference was possible

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• One study alone usually isnt enough to convince
  the scientific community
• Many more studies of Echinacea were done, some
  supported the collected data. some conflicted
  with the collected data
• As of now, the use of Echinacea as a cold
  treatment is not scientifically supported, even
  though it continues to be commonly used

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Scientific Method Lessons

• Using M M candy to learn about the Scientific
  Method
• http//www.scienceteacherprogram.org/genscience/AM
  eyer05.html
• Ant behavior and the Scientific Method
• http//biology.arizona.edu/sciconn/lessons2/Shinde
  lman/Objectives.htm