Non-experimental designs
Outline
1. Experimental vs. non-experimental
research
2. Four kinds of non-experimental
research:
–
–
–
–
Observational research
Archival research
Case studies
Surveys
1. Experimental vs. non-experimental
research
• Experimental research
requires exerting control.
• Experimenters exert
control through
manipulation and
assignment
1. Experimental vs. non-experimental
research
• Manipulation
• researcher systematically
varies conditions under
which participants perform
task
• “treatments”
1. Experimental vs. non-experimental
research
• Manipulation
• Assignment
• researcher decides who
gets which treatment
1. Experimental and non-experimental
research compared
• Non-experimental research
allows researcher much less
control
• No assignment
• In many cases, no
manipulation
1. Experimental and non-experimental
research compared
• Four approaches:
– Observational
• Recording ongoing behavior
without trying to influence
it.
1. Experimental and non-experimental
research compared
• Four approaches:
– Observational
– Archival
• Testing a hypothesis using
data that the researcher
did not collect
1. Experimental and non-experimental
research compared
• Four approaches:
– Observational
– Archival
– Case study
• Researcher carries out very
detailed examination of
individual cases
Experimental and non-experimental
research compared
• Four approaches:
– Observational
– Archival
– Case study
– Survey
• Researcher collects
information on beliefs,
attitudes, preferences,
behaviors, and their
correlations.
Observational Research
•
The researcher observes
behavior without
influencing it.
• Goals:
– to describe behavior as it
naturally occurs
Observational Research
•
The researcher observes
behavior without
influencing it.
• Goals:
– to describe behavior as it
naturally occurs
– to assess relationships among
variables present
Observational Research
• Four approaches to nonexperimental research:
– Observational
– Archival
– Case study
– Survey
• Four approaches to
observation:
i. Naturalistic observation
ii.Participant-observer
research
iii.Structured observation
iv.Field experiments
Observational
Naturalistic
Archival
Participantobserver
Case Study
Structured
observation
Survey
Field
experiments
Naturalistic Observation
•
Observing phenomena that
cannot be created in lab, for
practical or ethical reasons
•
Effects can be observed
when such events occur
naturally
Naturalistic Observation
•
Physical trace measures
– e.g., how “well-thumbed” is
a book?
– Where do paths through the
snow go?
•
Reactivity
– subjects react to the
presence of the observer
Naturalistic Observation
•
Example: effect of early
childhood isolation on later
psychological development.
•
We can’t isolate children to
study them
•
But we can use naturalistic
observation when we
discover such cases
Naturalistic observation
• Candland (1993) –
descriptions of feral
children (raised outside
human cultures)
• Curtiss (1977) case studies
of children subjected to
unusual isolation by parents
(e.g., Genie)
• Spitz (1965) – observation
of institutionalized children
– Showed effects of deprivation
of stimulation during infancy
and early childhood
Observational Research
• Four approaches to
observation:
i. Naturalistic observation
ii.Participant-observer
research
iii.Structured observation
iv.Field experiments
Participant-observer research
• Observer joins a group for
the purpose of studying
group members
• Undisguised vs. disguised
• Why use disguised
observation?
– Access to behavior and
situations
Participant-observer research
• Observer joins a group for
the purpose of studying
group members
• Potential cost to
objectivity
– Stockholm syndrome
Observational Research
• Four approaches to
observation:
i. Naturalistic observation
ii.Participant-observer
research
iii.Structured observation
iv.Field experiments
Structured observation
• Researcher exerts some
control
– Eleanor Gibson’s visual cliff
studies
– Piaget’s studies
• Replication depends upon
following exactly the same
procedures
Observational Research
• Four approaches to
observation:
i. Naturalistic observation
ii.Participant-observer
research
iii.Structured observation
iv.Field experiments
Field experiments
• Researcher manipulates
one or more variables in a
natural setting to
determine effect on
behavior
• One end of the
intervention – nonintervention continuum
Field experiments example
• Crusco & Wetzel (1984)
• effect of touching on
restaurant customers
• waitresses worked as
confederates
• tip amount was
dependent variable
Field experiments example
• Crusco & Wetzel (1984)
• Compared No Touch
condition with Fleeting
Touch and Shoulder Touch
conditions
• Men tipped more than
women
• Both men and women
tipped more after being
touched at some point
during their meal.
Observational Research
• Four approaches to nonexperimental research:
– Observational
– Archival
– Case study
– Survey
•
Testing a hypothesis using
data that the researcher did
not collect
b. Archival Research
• Archival records are a rich
source of data
– No possibility of reactivity
– Often very inexpensive
approach
•
•
•
•
•
•
Government files
Corporations
Universities
Newspapers
Google cache
Internet wayback machine
b. Archival Research – an example
• Lau & Russell (1980)
– Tested external validity of
laboratory findings on
causal attributions
•
People make internal
attributions for success and
external attributions for
failure
Lau & Russell (1980)
•
Sports pages in 8 daily
newspapers
• Found 594 explanations for
success and failure involving
33 sports events
•
Proportions of internal
attributions:
•
•
success – 75%
failure – 45%
Case Studies
• Intensive studies of
individual cases.
– Strength: you learn a lot
about the case studied
– Weakness: results may not
generalize
•
We’ll come back to this
topic when we look at
Single-Subject
Experiments.
Surveys - Definition
•
A procedure for
systematically collecting
data on attitudes,
preferences, knowledge, or
behavior by asking people
questions.
• The answers provide
information about the
group(s) that those people
represent.
d. Surveys
•
Use surveys when:
– You want data regarding a
large group of people (a
population)
– Measuring whole
population is too expensive
in time, money or other
resources
• Population = all the cases
of interest
Surveys
• We’ll look at surveys in
greater detail in the next
lecture…