Unit 2 Experimentation
Or How do psychologists get
all that data to support their
theories???
Psychological studies…
 Provide
broad scientific
information
 Explain what we do
 Tell us why we do it
 and tell us what changes
occur over time!!!
Accurate experiments…
Give
us solid
information
Allow psychologists to
support theories about
behavior
Psychologists get data using…
 Surveys
 Case
Studies
 Naturalistic observation
 Interviews
 Cross-sectional studies
 Longitudinal studies
Most methods use…
Sample groups
 (def.-group that represents a
larger group)
 WHY??? Because its too
expensive and takes too much
time to get data from everyone
in the whole wide world (even
with the internet!!!)

Why do psychologists need so
many methods??
Because some work better than
other in different situations
 Interview– face to face
questions
 Survey- answer questions
usually anonymously
 Advantage/disadvantage of
each???

All psychologists use …
 The
Scientific Method!!!
 Which
is defined as the
procedure to gather and
interpret data
BUT… EXPERIMENTATION
Is the most used method by
psychologists to gather data
 Experiments are a causal
relationship between two
variables or stated this way…

IF
X , THEN Y
TWO types of experiments are…

Laboratory – done in a lab
(DUH!!!)

Field – conducted out in the real
world

What are the advantages and
disadvantages of each????
Elements of experiments:
Hypothesis- an educated guess
 Subjects- people on which the
experiment is conducted
 Variables- factors in the
experiment (psychologists try to
identify and control the
variables)

Types of Variables…



Independent variable: has an
effect on other variables (is messed
with by the psychologist)
Dependent variable: changes in
an experiment so it is always
measured!!!
Hidden variables– unwanted
variables that if not detected can
change the results
Exploring Cause & Effect
Many factors influence our behavior. Experiments
(1) manipulate factors that interest us, while other
factors are kept under (2) control.
Effects generated by manipulated factors isolate
cause and effect relationships.
Placebos…
Has no active ingredients
 Sometimes called “the sugar
pill”
 Can also work by the power of
suggestion ( mind over matter)
 Up to 30% of people on
placebos get better (who’d have
thought that!!!)

Subjects are put into groups..
Experimental group- gets the
active ingredient (the IV)
 Control group- gets the
placebo
 WHY?? So psychologists can
compare the two !!!

Bias can come from…




“Hidden” or confounding variables
Participant bias- when the subjects
try to influence the results either
deliberately or accidentally
Researcher Bias- when the
psychologist influences the results
either deliberately or accidentally
Results in “bad” data
How do we know if the
results are good?????
Replication!!!!
If
an experiment can
be repeated with the
same results… the
hypothesis is good.
Correlation
When one trait or behavior accompanies another,
we say the two correlate.
Indicates strength
of relationship
(0.00 to 1.00)
Correlation
coefficient
Correlation Coefficient is a statistical
measure of the relationship between
two variables.
r = + 0.37
Indicates direction
of relationship
(positive or negative)
Correlation and Causation
Correlation does not mean causation!
or
Illusory Correlation
The perception of a relationship where no relationship
actually exists. Parents conceive children after adoption.
Do not conceive
Adopt
Confirming
evidence
Disconfirming
evidence
Do not
adopt
Disconfirming
evidence
Confirming
evidence
Michael Newman Jr./ Photo Edit
Conceive
Exploring Cause & Effect
Many factors influence our behavior. Experiments
(1) manipulate factors that interest us, while other
factors are kept under (2) control.
Effects generated by manipulated factors isolate
cause and effect relationships.
Experimentation
A summary of steps during experimentation.
Comparison
Below is a comparison of different research methods.