Review of the Scientific Method

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Review of the Scientific Method

• "The scientific method is nothing but the normal
  working of the human mind."
• Thomas Huxley

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What is the Scientific Method?

• The scientific method is a planned, logical,
  approach taken to solving a problem
• It consists of asking a question, developing a
  possible solution, testing the possible solution,
  recording data, and analyzing results

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Steps of the Scientific Method

• The basic scientific method consists of five
  broad steps
• Identifying the problem or question
• Developing a possible solution, or hypothesis
• Designing and executing a test
• Collection and analysis of data
• The formulation of a conclusion

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Identifying the Problem or Question

• Identify a problem to be solved or a questioned
  to be answered.
• To be scientifically valid, questions or problems
  must be falsifiable.
• Usually scientists collect information about a
  problem or question, before positing a possible
  solution.
• The possible solution to a scientific problem or
  question is known as a hypothesis

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The Hypothesis

• A hypothesis is a possible solution to a
  scientific problem or question.
• To be valid a hypothesis must be testable
• Ex. Which of the following are valid hypotheses?
• The sky is blue due to the reflection of
  sunlight off the Earths oceans.
• The sky is blue due to the scattering of blue
  light by oxygen in the atmosphere.
• The sky is blue because a higher being made
  it that way.

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Procedure What is an Experiment?

• An experiment is a test designed to prove or
  disprove a hypothesis
• Experimental Design involves
• Establishing controlled and uncontrolled
  variables
• Establishing the independent and dependent
  variables.
• Experiments generate data which scientists record
  in tables, etc.

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Collecting and Analyzing Data

• Data collection occurs as an experiment proceeds.
• Usually data is numerical in form
• However, during an experiment observations may be
  made that can include temperature changes, the
  formation of gas bubbles, changes in color, etc.

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Analysis of Data

• Numerical Data is usually analyzed by determining
  the mean, median, and mode.
• Numerical data is often graphed as a means of
  visually determining relationships between
  variables.

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Conclusions

• After the data is analyzed a determination must
  be made as to whether the data supports or
  refutes the hypothesis.
• If the data supports the hypothesis
• If the data refutes the hypothesis
• If the data is indeterminate

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An Example of Experimental Design

• Francesco Redi
• Tests the Theory of
• Spontaneous
• Generation

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Background Spontaneous Generation

• Until the seventeenth century experimentation was
  treated as an art rather than science.
• Many strange, and now discredited, ideas about
  how living organisms are propagated flourished.
• The theory of spontaneous generation was a very
  popular, ancient theory used to explain the
  seeming production of many animals from
  non-living materials.

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Example One

• Observation Every year in the spring, the Nile
  River flooded areas of Egypt along the river,
  leaving behind nutrient-rich mud that enabled the
  people to grow that years crop of food. However,
  along with the muddy soil, large numbers of frogs
  appeared that werent around in drier times.
• Conclusion It was perfectly obvious to ancient
  peoples that the muddy soil gave rise to the
  frogs.

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Example Two

• Observation In many parts of Europe, medieval
  farmers stored grain in barns with thatched
  roofs. As a roof aged, it was not uncommon for it
  to start leaking. This could lead to spoiled or
  moldy grain, and of course there were lots of
  mice around.
• Conclusion It was obvious to them that the mice
  came from the moldy grain.

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Example Three

• Observation Since there were no refrigerators,
  the mandatory, daily trip to the butcher shop,
  especially in summer, meant battling the flies
  around the carcasses. Typically, carcasses were
  hung by their heels, and customers selected
  which chunk the butcher would carve off for them.
  Many times they would have to remove maggots from
  the putrefying meat.
• Conclusion Obviously, the rotting meat that had
  been hanging in the sun all day was the source of
  the maggots and flies

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Redis Experiment

• Francesco Redi (1626-1697), an Italian scientist,
  thought that the Theory of spontaneous Generation
  was incorrect.
• In 1668 he designed what is thought to be the
  first experiment explicitly designed via the
  scientific method.
• The experiment tested the idea that maggots, and
  therefore flies, are generated spontaneously from
  rotting meat.

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Redis Problem and Hypothesis

• Observation There are flies around meat
  carcasses at the butcher shop.
• Question Where do the flies come from? Does
  rotting meat turn into, or generate, the flies?
• Hypothesis Rotten meat does not turn into flies.
  Only flies can make more flies.
• Prediction If meat cannot turn into flies,
  rotting meat in a sealed (fly-proof) container
  should not produce flies or maggots.

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Redis Test and Observations
Data Presence or absence of flies and maggots
observed in each jar was recorded. In the control
group of jars, flies were seen entering the jars.
Later, maggots, then more flies were seen on the
meat. In the gauze-covered jars, no flies were
seen in the jars, but were observed around and on
the gauze, and later a few maggots were seen on
the meat. In the sealed jars, no maggots or flies
were ever seen on the meat.
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Redis Conclusions

• Only flies can make more flies.
• In the uncovered jars, flies entered and laid
  eggs on the meat. Maggots hatched from these eggs
  and grew into more adult flies.
• Adult flies laid eggs on the gauze on the
  gauze-covered jars. Maggots appeared on the
  gauze.
• In the sealed jars, no flies, maggots, nor eggs
  could enter, thus none were seen in those jars.
• Maggots arose only where flies were able to lay
  eggs. This experiment disproved the idea of
  spontaneous generation for larger organisms.

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Controlled Versus Uncontrolled Variables

• A controlled variable is any factor in an
  experiment that is kept the same in all trials of
  the experiment.
• Controlled variables are more commonly known as
  Constants.
• Uncontrolled variables are those factors in an
  experiment that are allowed, or chosen, to change
  during the experiment.
• There are two types of uncontrolled variables
  Independent and Dependent

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Independent versus Dependent Variables

• The independent variable (aka manipulated
  variable) is the factor in an experiment that is
  chosen, or manipulated by the experimenter.
• What was the independent variable in Redis
  experiment?
• The dependent variable (aka responding or
  measured variable) in an experiment is the factor
  that changes or responds to changes in the
  independent variable.
• What was the dependent variable in Redis
  experiment?

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Control Group versus Experimental Group

• The control group in an experiment is the set of
  tests in which nothing was manipulated by the
  experimenter.
• The control group is the standard by which all
  changes in the manipulated tests are measured.
• What was the control group in Redis experiment?
• The experimental group in an experiment is the
  set of tests in which the experimenter
  manipulates the independent variable.
• What was the experimental group in Redis
  Experiment?

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Identifying Controls and Variables

• Smithers thinks that a special juice will
  increase the productivity of workers.
• He creates two groups of 50 workers each and
  assigns each group a task (in this case theyre
  supposed to staple a set of papers).
• Group A is given the special juice to drink while
  they work. Group B is not given anything.
• After one hour Smithers counts how many stacks of
  papers each group has made. Group A made 1,587
  stacks, Group B made 2,113 stacks.

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Identifying Controls and Variables

• What was Smithers
• Control Group?
• Independent Variable?
• Dependent Variable?
• What should Smithers conclusion be?
• How could Smithers improve his experiment?

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Assignment

• Work in pairs to complete The Simpsons
  Identifying Controls and Variables worksheet.
• If you do not finish the assignment in class
  complete it as home work.

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Yesterdays Classwork/Homework

• Identifying Experimental Variables and Controls