Psychology Research Methods

Characteristics of Good Psychological Research © 2002 John Wiley & Sons, Inc.

Psychological Research 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 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 © 2002 John Wiley & Sons, Inc.

Correlational Research Establishes whether there is a relationship between two or more variables CANNOT INFER CAUSALITY 1.Directionality problem 2.Potential for a third variable (confound)

Self EsteemGPA Third Variable (Confound) E.g., High IQ

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 pre- existing 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