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