Scatter Diagram OR Dot Method Scattered diagram we

Scatter Diagram OR Dot Method Scattered diagram- we may study a form of association between two variables with the help of a scatter diagram. In a scatter diagram we plot the value of the two variable on a graph paper as a set of points, On a points, so obtained, is called scatter diagram.

The scatter diagram can be interpreted in the following way : (1) If the plotted points show upward trend from the lower left – hand corner to the upper right – hand corner of the diagram. Y Shows perfect positive correlation =R = 1 0 x (2) The correlation is perfectly negative ( Where r = -1) if all the items lie on a straight - line rising from the upper left – hand corner to the lower right – hand corner of the diagram. Y Shows perfect Negative correlation =R = -1 0 X

Scatter diagram (3) Rising tendency of plotted points – from the left – hand corner and move higher towards the right – hand corner. Y Shows positive correlation 0 x (4) Declining tendency of the plotted points from right – hand corner to the left hand corner. Y Shows Negative correlation 0 X

Scatter diagram (5) If the plotted points show no trend at all , it shows absence of correlation Y Shows absence of correlation 0 x

Scatter diagram Example : You are given X & Y variable in the following manner : X 4 6 8 10 12 14 16 Y 8 10 12 14 16 18 20 Construct a scatter diagram and show – Is there any relation between X & Y variable ? Solution : Y 20 -----------------------------------------16 ------------------------12 - - - ------8 ------4 0 2 4 6 8 10 12 14 16 X

Merits of scatter diagram method (1) Simplicity : (2) Non – Mathematical : (3) Uninfluenced by the size of extreme items : Demerits of scatter diagram method (1) Non – Mathematical : (2) Degree of correlation unobtainable :