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Correlations. Relationships between variables. Correlation Coefficient. Numerical index that reflects the relationship between 2 variables Ranges from –1 to +1 Pearson product-moment correlation or Pearson’s r. Types of correlations. Positive or direct correlation
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Correlations Relationships between variables
Correlation Coefficient • Numerical index that reflects the relationship between 2 variables • Ranges from –1 to +1 • Pearson product-moment correlation or Pearson’s r
Types of correlations • Positive or direct correlation • 2 variables move in the same direction • Scores range: • 0 (no correlation) to +1.0 (perfect correlation) • Negative or indirect correlation • 2 variables more in the opposite direction • Scores range: • 0 (no correlation) to –1.0 (perfect correlation)
Scatterplot • Illustrates the relationship between variables • X on the horizontal axis • Y on the vertical axis • Positive correlation • Data from lower left to upper right • Negative correlation • Data from upper right to lower left
Multiple correlationsAKA correlation matrix • Shows correlations between multiple variables • Series of bivariate correlations