Correlation: The
Scatter Diagram


The simplest way to reveal a possible correlation between bivariate data is to express it graphically.  Let's use the example from the preceding page:

x

24

15

17

32

19

18

25

34

y

22

11

14

30

17

12

23

31

Apparently there is a strong linear relationship with the points, one that follows an upward moving pattern. If we were to join the points with a line, it would possess a positive slope, representing a positive relationship. Other examples of scatter diagrams help illustrate relationships between points.

Scatter diagrams are helpful in that they do not require complex calculations. A more precise method of discovering a relationship is to make apply the linear correlation coefficient

Linear Correlation Coefficient


 

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