Scatter Diagram of Bivariate
Measurement Data
Bivariate Measurement Data
Example of Bivariate Measurement:
Some questions for Bivariate Data
• Are the variables related?
• Can we quantify the strength of their relationship?
• Can we predict one variable from the other?
• Let x, y be the two variables of a bivariate data.
• The variable x is marked along the horizontal axis and y on the vertical
axis on a graph paper.
• The pairs (x, y) of observations are then plotted as dots on the graph.
• The resulting diagram is called a scatter diagram or scatter plot.
The correlation Coefficient
• If the scatter plot of (x,y) is a line, we say x and y has a linear relation.
• The to measure how “linear” a relation is, we use the correlation
coefficient.
The correlation Coefficient, r
• The value of r is always between -1 and 1.
• The magnitude of r indicates the strength of a linear relation, whereas
its sign indicates the direction.
Calculation r