
Scatter plot  X Y chart
Graph used to show relationship or correlation
between two factors or variables. i.e. XY or XY or X Y chart. (can
be used in conjunction with correlation
coefficient below)
Each factor or variable should be drawn
on a graph, (a piece of grid paper would work), with X plotted
on the vertical axis and Y plotted on the horizontal axis, or
visaversa. Each factor or variable should be graphed in such a way
that they intersect both axis making one point for each of the XY
paired numbers.
Scatter Plot XY
Example Chart
The output is the degree of similarity
between two data sets. The calculation is below. (be sure to see precautions
to observe below)
As an example, data indicated that when
teachers are unemployed, the alcohol consumption rises. In that case,
there was no correlation.
Meaning of (r) in the
Correlation Coefficient
Relationship
Between X and Y 

r
= + 1.0 
Strong
 Positive 
As
X goes up, Y always also goes up 
r
= + 0.5 
Weak
 Positive 
As
X goes up, Y tends to usually also go up 
r
= 0 

No Correlation  
X
and Y are not correlated 
r
=  0.5 
Weak
 Negative 
As
X goes up, Y tends to usually go down 
r
=  1.0 
Strong
 Negative 
As
X goes up, Y always goes down 



Be careful when using the correlation
coefficient. One should think about the following rules.
Not all can see the relation between
the scatter plot and the correlation coefficient, but it can aid in
evaluations of a process.

