Scientific Method

					Scientific Method
       • .
            Important Terms
•   Independent variable – A manipulated
    variable in an experiment or study whose
    presence or degree determines the change in
    the dependent variable.
•   Dependent variable - The observed variable
    in an experiment or study whose changes are
    determined by the presence or degree of one
    or more independent variables.
•   Control - the factor being tested is not applied.
•   Placebos are generally characterized as inert
    substances or formulations, sham treatments,
    or inactive procedures.
         Important Terms
• Hypothesis - A tentative explanation for
  an observation, phenomenon, or scientific
  problem that can be tested by further
    Some Basic Components and
    Behaviors of System Models
•   A feedback loop occurs when one change produces some other
    change, which reinforces or slows the original change. They occur
    when an output of matter, energy or information is fed back into the
    system as input.
•   Positive feedback loop is a runaway cycle in which a change in a
    certain direction provides information that causes a system to change
    further in the same direction.
•   Negative feedback loop occurs when one change leads to a lessening
    of that change.
•   Homeostasis - the maintenance of favorable internal conditions
    despite fluctuations in external conditions. Homeostatic systems
    consist of one or more
•   Negative feedback loops that help maintain constant internal conditions
    when changes occur.
-Use senses for information
-We use INSTRUMENTS to extend the
Scientific Method Do’s & Don’t’s
• Do have only one independent variable during an
• Do repeat the experiment more than once to verify your
• Do have a control.
• Do have more than one control, with each being identical.
• Do organize data.
• Do state facts from past experiences or observations on
  which you base your hypothesis.
• Do write down your hypothesis before beginning the
  project experimentation.
• Don't change your hypothesis even if experimentation
  does not support it. If time permits, repeat or redesign the
  experiment to confirm your results.
• Don't leave out experimental results that do not support
  your hypothesis.
• There are different terms used to describe scientific ideas based on
  the amount of confirmed experimental evidence.
   - a statement that uses a few observations
   - an idea based on observations without experimental evidence
   - uses many observations and has loads of experimental evidence
   - can be applied to unrelated facts and new relationships
   - flexible enough to be modified if new data/evidence introduced
   - stands the test of time, often without change
   - experimentally confirmed over and over
   - can create true predictions for different situations
   - has uniformity and is universal
   You may also hear about the term "model." A model is a scientific
   statement that has some experimental validity or is a scientific
   concept that is only accurate under limited situations. Models do
   not work or apply under all situations in all environments. They are
   not universal ideas like a law or theory.
Scientific Theories and Laws:
The Most Important Results of
                • Scientific Theory
                  – Widely tested and
                • Scientific Law
                  – What we find
                    happening over and
                    over again in
• Variables are what affect processes in the
• Controlled experiments have only one variable
• Experimental group gets the variable
• Control group does not have the variable
  – Placebo is a harmless pill that resembles the pill
    being tested.
  – In double blind experiments, neither the patient nor
    the doctors know who is the control or experiment
  The Scientific
Method involves a
series of steps that
    are used to
   investigate a
  Formulate a Hypothesis
Collect and Analyze Results
 Communicate the Results
      Steps of the
    Scientific Method
1. Problem/Question: Develop a
   question or problem that can
        be solved through
     Steps of the
   Scientific Method
2. Observation/Research: Make
   observations and research
      your topic of interest.
Do you remember the
     next step?
    Steps of the
  Scientific Method
 3. Formulate a Hypothesis:
 Predict a possible answer to
   the problem or question.
Example: If soil temperatures
  rise, then plant growth will
           Testing Hypotheses
• Scientists test hypotheses using controlled experiments
  and constructing mathematical models.
   – Variables or factors influence natural processes
   – Single-variable experiments involve a control and an
     experimental group.
   – Most environmental phenomena are multivariable
     and are hard to control in an experiment.
      • Models are used to analyze interactions of
      Steps of the
    Scientific Method
  4. Experiment: Develop and
       follow a procedure.
Include a detailed materials list.
     The outcome must be
    measurable (quantifiable).
      Steps of the
    Scientific Method
5. Collect and Analyze Results:
     Modify the procedure if
Confirm the results by retesting.
  Include tables, graphs, and
   Steps of the
 Scientific Method
 6. Conclusion: Include a
 statement that accepts or
   rejects the hypothesis.
Make recommendations for
 further study and possible
    improvements to the
      Steps of the
    Scientific Method
7. Communicate the Results: Be
 prepared to present the project
        to an audience.
   Expect questions from the
Think you can name all
     seven steps?

 Formulate a Hypothesis
  Communicate the Results
Collect and Analyze Results
   Formulate a Hypothesis
   After talking with his
        teacher and
     conducting further
    research, he comes
   up with a hypothesis.
“If more sugar is added,
  then the bread will rise
The hypothesis is an educated
  guess about the relationship
 between the independent and
      dependent variables.
Note: These variables will be
 defined in the next few slides.
Do you know the difference
 between the independent
and dependent variables?
  Independent Variable
      The independent, or
    manipulated variable, is a
 factor that’s intentionally varied
      by the experimenter.
John is going to use 25g., 50g.,
 100g., 250g., 500g. of sugar in
          his experiment.
   Dependent Variable
 The dependent, or responding
  variable, is the factor that may
  change as a result of changes
     made in the independent
In this case, it would be the size
        of the loaf of bread.
His teacher helps him
    come up with a
 procedure and list of
  needed materials.
 She discusses with
      John how to
 determine the control
       Control Group
  In a scientific experiment, the
 control is the group that serves
 as the standard of comparison.
The control group may be a “no
 treatment" or an “experimenter
          selected” group.
      Control Group
The control group is exposed to
   the same conditions as the
 experimental group, except for
    the variable being tested.
All experiments should have a
          control group.

The constants in an
experiment are all the
    factors that the
experimenter attempts
  to keep the same.
     Scientific Reasoning and
• Inductive reasoning
  – Involves using specific observations and
    measurements to arrive at a general
    conclusion or hypothesis.
  – Bottom-up reasoning going from specific to
• Deductive reasoning
  – Uses logic to arrive at a specific conclusion.
  – Top-down approach that goes from general to
Frontier Science, Sound Science,
        and Junk Science
• Frontier science has not been widely
  tested (starting point of peer-review).
• Sound science consists of data, theories
  and laws that are widely accepted by
• Junk science is presented as sound
  science without going through the rigors of
   Frontier and Consensus
• Frontier Science
  – Scientific “breakthroughs” and controversial
    data that has not been widely tested or
  – String Theory
• Consensus or Applied Science
  – Consists of data, theories, and laws that are
    widely accepted by scientists considered
    experts in the field involved
  – Human Genome Project
  Limitations of Environmental
• Inadequate data and scientific
  understanding can limit and make some
  results controversial.
  – Scientific testing is based on disproving rather
    than proving a hypothesis.
     • Based on statistical probabilities.
        Feedback Loops:
     How Systems Respond to
• Outputs of matter, energy, or information fed
  back into a system can cause the system to
  do more or less of what it was doing.
  – Positive feedback loop causes a system to
    change further in the same direction (e.g.
  – Negative (corrective) feedback loop causes a
    system to change in the opposite direction (e.g.
    seeking shade from sun to reduce stress).
          Feedback Loops:
• Negative feedback can take so long that a
  system reaches a threshold and changes.
  – Prolonged delays may prevent a negative
    feedback loop from occurring.
• Processes and feedbacks in a system can
  (synergistically) interact to amplify the
  – E.g. smoking exacerbates the effect of
    asbestos exposure on lung cancer.
           Feedback Loops
• A feedback loop
  occurs when an
  output of a system is
  fed back as an input
• Two kinds of
  feedback loops
  – Positive
  – Negative
        System Regulation
Positive Feedback     Homeostasis

Negative Feedback      Time Delay

                           Fig. 3-3 p. 46
• A system is a set of components that
  function and interact in some regular
  and predictable manner
• It has a structure and a function
  – The earth is a closed system for matter
    and an open system for energy
• Usefulness of models
  – Complex systems are predicted by developing
    a model of its inputs, throughputs (flows), and
    outputs of matter, energy and information.
  – Models are simplifications of “real-life”.
  – Models can be used to predict if-then
  Scientific Models - Mental
• Mental models
  help people
  perceive the
  world, control
  their bodies and
  – Working model of
    a car engine
    while you are
    trying to
    diagnose a
        Conceptual Models
• Describes general relationships among
  components of a system.
           Graphic Models
• Compile and display data in meaningful
           Physical Models
• Miniature versions of large systems that
  are made to test out designs and ideas.
        Mathematical Model
• Consists of one or more mathematical
  equations to describe the behavior of a

Shared By: