The Scientific Method Chapter 2

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					  The Scientific Method

                Chapter 2

         Manuel Gomez-Ramirez
CCNY (Experimental Psychology Spring 2007)
                          Scientific Method

•    It is based on gathering         General        Empirical
    observable, empirical,            Approach:
    measurable evidence, subject to
    the principles of reasoning.      Observation:   Systematic and
•   There are several modules that    Reporting:     Unbiased and
    make up the scientific method:                   objective
                                      Concepts:      Clear operational
     –   Observation                                 definitions
     –   Question
                                      Instruments:   Accurate and
     –   Prediction
     –   Testing
     –   Analysis                     Measurement:   Valid and reliable
     –   Conclusion
                                      Hypotheses:    Testable

                                      Attitude:      Critical and
                        Scientific Method

• Characteristics:

   – Observation: A good scientist is observant and notices things in the
     world. He/she notices what’s going on in the world and becomes curious
     about what’s happening. This can include reading and studying what
     others have done.

       • Question: The scientist then raises a question about what’s going
         on. The question raised must have a “simple,” concrete answer that
         can be obtained by performing an experiment.

       • Hypothesis: This is a tentative answer to the question. A testable
         explanation for what was observed. A hypothesis is formed in terms
         of dependent and independent variables.

   – Concepts: we use them to give meaning to things. Scientists give
     meaning to a concept by defining it operationally. That is, an operational
     definition explains a concept solely in terms of the operations used to
     produce and measure it.
                    Scientific Method

• Characteristics:

  – Reporting: when scientists report their findings, they seek to
    separate what they have observe from what they conclude or
    infer on the basis of observations.
      • It needs to be unbiased and objective

  – Instruments: they are used to measure events.
      • An input – output system.
      • Measurements can be made by varying the levels of
      • They are needed to make accurate measurements
          – Personal equation problem!!!
                     Scientific Method

• Characteristics:

   – Measurements: they provide the record of the experiment.
     Scientists use instruments to obtain measurements. Types of
     measurements include:
      • Physical measurements (i.e. velocity, acceleration, voltages)
      • Psychological measurements (used for rating beauty,
        aggression, intelligence, etc.)

       • Measurements NEED to be reliable and valid.

   – Hypothesis: a tentative explanation for something.

       • They should be always testable!!
       • Hypothesis are not testable if the concepts to which they
         refer are not adequately defined (i.e. bad operational
                  Scientific Method

• Characteristics:

  – Attitude: the mind-set of scientists needs to be skeptic,
    especially with regards to new and fascinating discoveries.

     • Being skeptical leads to be more cautious, thus leaving
       less room for errors (i.e. confounds etc)
     • However, being skeptical does not entail disbelieving
       claims automatically (i.e. first-hand).
     • There’s a need for replication
             Scientific Method

• Goals of the scientific method:

  – Description
  – Prediction
  – Understanding
  – Creating change
                 Scientific Method

• Description:

  – Refers to the procedures researchers use to define,
    classify, or categorize events and their relationships.

     • DSM-IV to diagnose mental disorders

     • ASCII (American Standard Code for Information
       Interchange), which is the numerical representation of
       characters for computers.
                 Scientific Method

• Prediction:

  – Refers to the forecasting of an event given a set of
    one or more variables (i.e. f(x) = mx + b).

     • When scores of one variable can be used to predict scores
       on a second variable, then the two variables are correlated.

     • Correlation exists when two or more different measures of
       the events vary together, but…
     • Correlation does not mean causation!
                    Scientific Method

• Understanding:
   – Understanding is achieved when the causes of a phenomenon are
       • To understand a phenomenon a high degree of control over
         experiments is needed.
       • By conducting controlled experiments, scientists can make causal

       • Causal Inference:
           – Covariation of events
           – Time-order relationship
           – Elimination of plausible alternative causes (i.e. no confounds)
                » To have no confounds means that the study internal
                  Scientific Method

• Creating Change:

  – The practical implementation of the resolved question

  – Research on creating change is often called “applied research”

  – Applied research: scientists conduct research in order to change
    people’s lives for the better.

  – Basic research: seek primarily to understand behavior and
    mental processes.
                         Scientific Method
• Scientific Theory Construction and Testing:

   – Theories are proposed explanations for the causes of phenomena. They
     CAN be wrong, whereas “laws” are irrefutable facts that occur in the
     world (i.e Ohms Law)

   – A scientific theory is a logically organized set of propositions that
     describes events.

   – Theories are evaluated by judging its internal consistency, external
     consistency, and whether it makes precise predictions based on
     parsimonious explanations.

       • The rule of parsimony: the simplest of alternative explanations is accepted
         (i.e. SIMPLE IS GOOOOOOOOD)
                      Scientific Method
• A psychologist was interested in the effect of food deprivation on
  motor activity. She assigned each of 60 rats to one of four conditions
  differing in the length of time for which the animals were deprived of
  food: 0 hours, 8 hours, 16 hours, 24 hours. She then measured the
  amount of time the animals spent in the activity wheel in their cages.

• A physical education instructor was interested in specifying the
  changes in motor coordination with increasing age in young
  children. He selected six groups of children and gave each child a
  test of motor coordination. The groups of children differed in age,
  that is, on group was made up all 5 year olds, the next group was all
  6 year olds, and so on up to the sixth group, which was all 100 year