The Scientific Method

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The Scientific Method

• by Ozan Akkus, Ph.D.
• Fordham University
• August 2005

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Scientific Method
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Scientific Method
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Scientific Method Description

• Orderly and cautious means of building
  supportable, evidence-based understanding of the
  natural world
• observations
• hypotheses
• deductions
• theory
• explanations for natural phenomena
• experiments test predictions reproducibly

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Scientific Method History

• Egyptian period (15th century BC)
• Edwin Smith and Ebers Papyra, medical manuscripts
  (demons ?)
• Ancient Greece (5th century BC)
• Plato teaching of arithmetic, astronomy and
  geometry in schools
• Aristotle empiricism
• all human knowledge comes at first from senses
  and experience slice of apple
• denies that humans have innate ideas

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Scientific Method History

• Roger Bacon (13th Century)
• repeating cycle of observation, hypothesis,
  experimentation and the need for independent
  verification
• Francis Bacon (17th Century)
• "The understanding must not therefore be supplied
  with wings, but rather hung with weights, to keep
  it from leaping and flying. when it is done, we
  may entertain better hopes of the sciences."
• ..by successive steps not interrupted or broken,
  we rise from particulars to lesser axioms and
  then to middle axioms, one above the other and
  last of all to the most general

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Scientific Method History

• René Descartes (17th Century)
• "never to accept anything for true which I did
  not clearly know to be such . avoid
  precipitancy and prejudice, and to comprise
  nothing more in my judgment than what was
  presented to my mind...
• divide each of the difficulties under examination
  into as many parts as possible, and as might be
  necessary for its adequate solution.
• conduct my thoughts by commencing with objects
  the simplest and easiest to know, I might ascend
  by little and little to the knowledge of the more
  complex
• assured that nothing was omitted in every case to
  make enumerations so complete, and reviews so
  general"

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Scientific Method History

• Isaac Newton
• admit no more causes of natural things than such
  as are both true and sufficient to explain their
  appearances ? simple
• to the same natural effects we must, as far as
  possible, assign the same causes ? concept of
  theory, applies to the general
• The qualities of bodies are to be esteemed the
  universal qualities of all bodies whatsoever.
• look upon propositions collected by general
  induction from phenomena as accurately or very
  nearly true, notwithstanding any contrary
  hypotheses that may be imagined, till such time
  as other phenomena occur, by which they may
  either be made more accurate, or liable to
  exceptions.
• "To explain all nature is too difficult a task
  for any one man or even for any one age. 'Tis
  much better to do a little with certainty, and
  leave the rest for others that come after you,
  than to explain all things."

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Scientific Method Elements

• Characterization
• Hypothesis
• Prediction
• Experiment

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Scientific Method Elements

• Characterization
• Subject/problem/unknown
• Careful thought
• Definitions
• Observations
• Measurement
• Counting
• Lab
• Instrument
• Statistics

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Scientific Method Elements

• Characterization phase can require extended and
  extensive study, even centuries.
• thousands of years of measurements, from the
  Chaldean, Indian, Persian, Greek, Arabic and
  European astronomers, to record the precession of
  the planet Earth
• Newton condensed these measurements into
  consequences of his laws of motion.
• perihelion of the planet Mercury's orbit exhibits
  a precession which is not fully explained by
  Newton's laws of motion.
• observed difference for Mercury's precession,
  between Newtonian theory and relativistic theory
  was one of the first pieces of evidence for
  Einstein's theory of General Relativity.

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Scientific Method Elements

• Characterization (example)
• Gregor Mendel, mathematical basis of genetics
• the mechanism of the gene unclear
• Bragg's laboratory at Cambridge University made
  X-ray diffraction pictures of various molecules,
  starting with crystals of salt
• Using clues which were painstakingly assembled
  over the course of decades, beginning with its
  chemical composition, it was determined that it
  should be possible to characterize the physical
  structure of DNA, and the X-ray images would be
  the vehicle

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Scientific Method Elements

• Hypothesis development
• Assumption in the Greek
• A hypothesis is a suggested description of the
  subject
• A provisional idea whose merit is to be evaluated
• Requires work to be refuted or accepted
• Should be falsifiable
• Testable
• Confirmation does not imply that hypothesis is
  proven, remains provisional
• the form of a mathematical model
• X is greater than Y or Z decreases exponentially
  with W
• formulated as existential statement
• The globe is round
• DNA example the race to determine the structure
  of DNA
• Francis Crick and James Watson hypothesized that
  this molecule had a helical structure two
  intertwined spirals.
• Linus Pauling was hypothesizing a triple helix

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Scientific Method Elements

• Valid statements
• Chocolate may cause pimples.
• Salt in soil may affect plant growth.
• Plant growth may be affected by the color of the
  light.
• Bacterial growth may be affected by temperature.
• Ultra violet light may cause skin cancer.
• Temperature may cause leaves to change color.
• If we say "Trees will change color when it gets
  cold." we are making a prediction
• If we write, "Ultraviolet light causes skin
  cancer." could be a conclusion

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Scientific Method Elements

• Formalized Hypotheses
• A tentative relationship is stated
• One is "independent" and the other is
  "dependent."
• independent variable controlled by the scientist
• dependent variable the one that you observe
  and/or measure the results
• example If skin cancer is related to ultraviolet
  light , then people with a high exposure to UV
  light will have a higher frequency of skin
  cancer.
• If leaf color change is related to temperature ,
  then exposing plants to low temperatures will
  result in changes in leaf color.

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Scientific Method Elements

• As an example, someone who enters a new country
  and observes only white sheep, might form the
  hypothesis that all sheep in that country are
  white.
• Falsifiable (by observing a single black sheep)

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Scientific Method Elements

• Example of what is not a hypothesis
• Our hypothesis is that (or we propose that) by
  using a fiber optic probe we can detect cancerous
  lesions in the mucosa of the stomach. ?
  application
• Circular argument
• Limited knowledge, non-innovative

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Hypothesis Example

• Hypothesis
• Queen Isabella, I believe that the world is not
  flat, but round.
• Specific Aims (used to test the hypothesis)
• I will sail west to reach the East.

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Scientific Method Elements

• Prediction from the hypothesis
• useful hypothesis will enable predictions
• predict the outcome of an experiment or the
  observation of a phenomenon in nature
• essential that the outcome be currently unknown.
• the outcome known ? it's called a consequence
• If the predictions are not accessible by
  observation or experience, the hypothesis is not
  yet useful for the method,
• wait for others who might come afterward, and
  perhaps rekindle its line of reasoning based on a
  new technology or theory
• Edmund Halley's prediction of the year of return
  of Halley's comet which returned after his death.

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Scientific Method Elements
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Scientific Method Elements

• Prediction, DNA example
• When Watson and Crick hypothesized that DNA was a
  double helix, Francis Crick predicted that a
  X-ray diffraction image of DNA would show an
  X-shape

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Scientific Method Elements

• How to get about testing the hypothesis? ?
  experiments
• The specific aims state what you want to do in
  the order in which you want to do it
• Think of your aims as experiments designed to
  test your hypotheses

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Scientific Method Elements

• Ranking Criteria
• Most scientifically sound
• Can I test this?
• Can I narrow down the field of hypotheses?
• Time/cost to achieve outcome
• How easy/hard is the experiment
• Equipment, environment, and expertise available?

• Testing
• Method to be used does it test my hypothesis?
• How many measurements do I need?
• What controls do I need?
• How long will this take?
• data collection
• data analysis
• Will the results be definitive?

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Scientific Method What to do with your data?

• It does not matter if the results of your
  experiment are what you predicted
• Am I using the best tools?
• Do I need to revise my experimental design?
• Negative data is valuable
• Does the data lead to new experiments?

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Scientific Method Elements

• Iteration
• some consideration will lead the scientist to
  repeat an earlier part of the process
• failure to develop an interesting hypothesis ?
  re-define the subject they are considering
• failure of a hypothesis to produce interesting
  and testable predictions ? reconsideration of the
  hypothesis or the subject
• Failure of the experiment to produce interesting
  results ? reconsidering the experimental method,
  the hypothesis or the definition of the subject

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Scientific Method Elements

• Verification
• results must be reproduced by others within the
  science community
• Georg Wilhelm Richmann killed by ball lightning
  to his forehead (1753) when attempting to
  replicate the 1752 kite experiment of Benjamin
  Franklin

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Scientific Method Scope

• Scientific method
• can be applied to anything within the range of
  our experiences
• something has an effect on our lives
• can formulate theories and try to predict what
  this effect might be
• does not aim to give an ultimate answer.
  iterative and recursive nature ? it will never
  come to an end
• any answer it gives is provisional.
• cannot prove or verify anything in a strong sense

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Scientific Method Community

• Scientific community
• ensure the integrity of the scientific method
• Peer review evaluation
• scientific journals
• Scientist ? editor ? reviewer(s)
• Reviewer fellow (usually anonymous) scientists
• recommend publication, reject, publication with
  suggested modifications, or, sometimes,
  publication in another journal.
• serves to keep the scientific literature free of
  unscientific or crackpot work
• cut down on obvious errors
• improve the quality of the scientific literature
• peer review may inhibits the circulation of
  unorthodox work, and at other times may be too
  permissive

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Scientific Method Community

• reproduction and record-keeping
• common practice to repeat the experiments in
  order to duplicate the results
• further validating the hypothesis.
• debug systematic errors in experiments
• check for deliberate falsifications
• detailed records of their experimental procedures
• provide evidence
• effectiveness and integrity of the procedure
• assist in reproduction
• assist in the conception of new experiments
• Intellectual property

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