Page 173 - DMGT404 RESEARCH_METHODOLOGY

Unit 9: Correlation and Regression

Notes
Figure 9.1

Y Y

O X O X
Positive Linear Relationship Negative Linear Relationship
Y Y

O X O X
Non-Linear Relationship No Relation

If all the points or dots lie exactly on a straight line or a curve, the association between the
variables is said to be perfect. This is shown below:

Figure 9.2

Y Y Y

O X O X O X
Perfect Positive Perfect Negative Perfect Non-Linear
Linear Relationship Linear Relationship Linear Relationship

A scatter diagram of the data helps in having a visual idea about the nature of association
between two variables. If the points cluster along a straight line, the association between variables
is linear. Further, if the points cluster along a curve, the corresponding association is non-linear
or curvilinear. Finally, if the points neither cluster along a straight line nor along a curve, there
is absence of any association between the variables.
It is also obvious from the above figure that when low (high) values of X are associated with low
(high) value of Y, the association between them is said to be positive. Contrary to this, when low
(high) values of X are associated with high (low) values of Y, the association between them is
said to be negative.

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