The Pearson correlation coefficient measures the direction and strength of the linear relationship between __ quantitative variables.

The Pearson correlation coefficient measures the direction and strength of the linear relationship between two quantitative variables.

Step-by-step explanation:

1. Pearson correlation coefficient: This is a statistical measure that calculates the strength and direction of the linear relationship between two variables.
2. Measures the direction: It indicates whether the relationship between the variables is positive or negative.
3. Measures the strength: It quantifies how strong the linear relationship is between the two variables.
4. Linear relationship: This refers to a relationship that can be graphically represented as a straight line.
5. Two quantitative variables: The Pearson correlation coefficient specifically applies to two variables that are measured on a quantitative scale (i.e., numerical data).

So, the Pearson correlation coefficient measures the direction and strength of the linear relationship between two quantitative variables.