R is the ______ which ranges from -1 to +1 and indicates the strength and direction of a linear relationship.

• A. P-value
• B. Pearson correlation coefficient
• C. R-squared
• D. Slope

Answer: (B)

Pearson correlation coefficient, often denoted r, measures the strength and direction of a linear relationship between two continuous variables. It ranges from -1 to +1: values near +1 indicate a strong positive linear association (as one variable increases, the other tends to increase), values near -1 indicate a strong negative linear association (as one increases, the other tends to decrease), and values near 0 indicate little to no linear relationship. The sign tells you the direction, while the magnitude tells you how strong the linear link is.

This is different from R-squared, which is the square of the correlation and tells you the proportion of variance explained by the relationship, not its direction. It’s also different from the slope in regression, which describes how much the dependent variable changes with a one-unit change in the predictor. And a P-value relates to whether the observed correlation is statistically significant, not the strength or direction itself. The key idea is that r captures both how strong the linear association is and which way it goes.