Psychology
Research Methods
Characteristics of Good
Psychological Research
Psychological Research
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Naturalistic observation
Surveys
Case Study
Correlational
Experimental
Correlation
• A correlation is a measure of association between
two variables (-1 < r < +1)
• direction (positive vs. negative/inverse)
• strength
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perfect correlation (1.0)
strong (0.6 to 0.8)
moderately strong (0.3 to 0.5)
no correlation (0)
• cannot tell us about causation
The Correlation Coefficient
Correlational Research
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Establishes whether there is a relationship
between two or more variables
• CANNOT INFER CAUSALITY
1. Directionality problem
2. Potential for a third variable (confound)
Third Variable
(Confound)
E.g., High IQ
Self Esteem
GPA
Correlational vs. Experimental
Research
• Smoking is correlated with lung cancer
• High grades are correlated with successful
careers
• Eating Frosted Flakes is correlated with
lower cancer rates
• In Taiwan birth control use is correlated
with number of household appliances
Experimental Research
• Considered the most powerful tool for
determining causal relationships
• Random Assignment: ensures that every
participant has an equal chance of being
assigned to any of the conditions
• This minimizes the chance that a preexisting difference between groups is the
cause of the “experimental effect”
Bias in Research
• Sampling bias
• Placebo effects
• Social desirability bias
• Response sets
• Experimenter bias:
- double blind procedure