The Scientific Method
CCNY (Experimental Psychology Spring 2007)
• 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
Instruments: Accurate and
– Analysis Measurement: Valid and reliable
Attitude: Critical and
– 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.
– 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!!!
– Measurements: they provide the record of the experiment.
Scientists use instruments to obtain measurements. Types of
• 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
– 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
• Goals of the scientific method:
– Creating change
– 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.
– 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!
– 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
• 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
• 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
– Theories are evaluated by judging its internal consistency, external
consistency, and whether it makes precise predictions based on
• The rule of parsimony: the simplest of alternative explanations is accepted
(i.e. SIMPLE IS GOOOOOOOOD)
• 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