Correlation (Descriptive)

Correlation (Descriptive)

1. Correlation coefficient (e.g., r)

   • r quantifies the size and direction of the relationship between 2 variables
   • r is a descriptive line statistic, and can be affected by a number of factors

2. When there is a significant correlation between X and Y, all we can conclude is that X is "related" to Y

   • Correlations have got to make sense; that is, interpretable in theory

3. Spurious Correlations: Chance relationships between 2 variables,

4. Effect Size (r^2)

5. Assumptions

   • Independence of Observations: 1 person can only contribute 1 score
   • Bivariate Normality: The X and Y variables are normally distributed
   • A statistical test is valid if its assumptions about the data are met. The degree to which these assumptions are met will determine the degree to which the test is valid

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