Correlational Studies

When to use Correlational Designs

• When it is not possible to manipulate certain variables

• Conduct a pilot study (prior to experiment)

• Supplement other designs

• Increased external validity

Correlational Research

• Involves the measurement of multiple dependent variables (without manipulation) and an assessment of their relationship

• Goals:

  • To determine if different behaviors are connected (related) and occur together

  • To be able to predict a chance in one form observing change in the other (when there is a strong relationship)

Limitations of Correlational Designs

• Primary limitation: Correlation doesn’t imply causation

  • Can only answer descriptive and predictive research questions

  • Often do not know which variable occurred first

  • Lack of control

  • Third variable problem: presence of extraneous factor that affects dependent variable

    • Can decrease internal validity

    • People low in self-esteem are more likely to report depression (they have higher depression levels)

Pearson Correlation Coefficient (pearson’s r)

• Summarized the direction and strength of the relationship between two variables

  • Values range from r= -1.00 to r = +1.00

• The direction of the relationship is indicated by the sign of correlation coefficient

  • Positive r values indicate positive relationships

  • Negative r values indicate negative relationships

• The strength of the relationship indicated by the magnitude of correlation coefficient

  • Weak relationship: closet to 0.00

  • Strong: Closer to -1 or +1

Output and Write-Up for Correlation

• Results + Discussion