Research Methods
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• Research Question
– Does social exclusion increase aggression?
• Hypothesis: a testable proposition
– Social exclusion increases aggression.
• Research design
– Correlational?
– Experimental?
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Descriptive Research
• assesses the amount or average level of a given
variable in a population
– e.g., public opinion surveys
• What is the white male homicide rate in the South?
• informative, but not a hypothesis test
3
Correlational Research
• investigates whether changes in one variable are
related to changes in another variable
– What is the relationship between being from the
South and aggressive behavior?
• Informs of relationship between variables
• CORRELATION COEFFICIENT: -1 to 1
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Correlational Research
High
(Independent/Predictor Variable)
0%
(Dependent Variable)
(Dependent Variable)
0%
Low
100%
NEGATIVE
100%
POSITIVE
Low
High
(Independent/Predictor Variable)
5
Correlational Research
0%
(Dependent Variable)
100%
NONE
Low
High
(Independent/Predictor Variable)
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Correlational Research
• in the social sciences (Cohen, 1992)
– r = .50 (strong)
– r = .30 (moderate)
– r = .10 (small)
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Correlational Research
• strengths of this approach
–
–
–
–
can be a random sample
actual behavior
has good generalizability (i.e., external validity)
potential for numerous variables
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Correlational Research
• weakness of this approach
– cannot infer a cause-effect relationship
• factors for inferring causality
– association -- yes
– temporal priority -- no
– rule out a spurious relationship -- no
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Experimental Design
• characteristics
– manipulation of a variable
• solves the direction of causality problem
– randomly assign to conditions
• solves the 3rd variable problem
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An Example of an Experimental Study
• Spontaneous game of ball toss with other participants:
Inclusion status (IV1)
• 2 confederates, actual participant either included or
ostracized
• Listen to noise blasts (IV2)
• Either given control over onset (restored control) or onset
determined randomly (no control)
• Allocate hot sauce to other participant (DV)
• Dependent measure (aggression)
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Basic Terminology: Levels of Variables
• Applies to Independent Variables (IVs)
– Amount of Inclusion (IV 1)
– Included (LEVEL 1)
– Ostracized (LEVEL 2)
– Amount of Control (IV 2)
– None (LEVEL 1)
– Restored (LEVEL 2)
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Basic Terminology: Conditions
• A condition is a unique combination of levels of
IVs
• 2 IVs with 2 levels each
Amount of Control
Restored
None
Amount of Inclusion
Included
Ostracized
Each box is a condition
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Amount of Hot Sauce Allocated
(grams)
Main Effects vs. Interaction
30
25
20
Included
15
Ostracized
10
5
0
No Control
Restored Control
Amount of Control
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Main Effects vs. Interaction
• Main Effect: The overall effect of the independent
variable on the dependent variable, ignoring all other
independent variables.
– Do the levels of a given variable produce different
results (e.g., favor from confederate vs.
experimenter)?
– On a graph, look for parallel lines
– In a table, sum diagonals
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Main Effects vs. Interaction
• Interaction (2-way): Occurs when the effect of one
independent variable varies as a function of the level of
the other independent variable (moderator).
– Does the effect of one variable depend on the level
of another variable?
– On a graph, look for non-parallel lines
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Experimental Design
• strengths
– allows for causal conclusions to be made -- best test
of theory
• weaknesses
– not all questions are amenable to experiments
– concerns about generalizability
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Methodological Challenges
•
•
•
•
expectancy effects
demand characteristics of the situation
social desirability concerns
ethical dilemmas
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Mundane and Experimental Realism
• Mundane Realism
– The extent to which the research setting resembles
the real-world setting of interest.
• Experimental Realism
– The degree to which the experimental setting and
procedures are real and involving to the participant.
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