1.
Exploratory Data Analysis
1.3. EDA Techniques 1.3.3. Graphical Techniques: Alphabetic


Purpose: Check for Relationship 
A scatter plot (Chambers 1983) reveals relationships or association between two variables. Such relationships manifest themselves by any nonrandom structure in the plot. Various common types of patterns are demonstrated in the examples.  
Sample Plot: Linear Relationship Between Variables Y and X 
This sample plot of the Alaska pipeline data reveals a linear relationship between the two variables indicating that a linear regression model might be appropriate. 

Definition: Y Versus X 
A scatter plot is a plot of the values of Y versus the
corresponding values of X:


Questions 
Scatter plots can provide answers to the following questions:


Examples 


Combining Scatter Plots 
Scatter plots can also be combined in multiple plots per page to
help understand higherlevel structure in data sets with more than
two variables.
The scatterplot matrix generates all pairwise scatter plots on a single page. The conditioning plot, also called a coplot or subset plot, generates scatter plots of Y versus X dependent on the value of a third variable. 

Causality Is Not Proved By Association 
The scatter plot uncovers relationships in
data. "Relationships" means that there is some structured
association (linear, quadratic, etc.) between X and Y.
Note, however, that even though
causality implies association
association does NOT imply causality.


Appearance 
The most popular rendition of a scatter plot is
Other scatter plot format variants include
In both cases, the resulting plot is referred to as a scatter plot, although the former (discrete and disconnected) is the author's personal preference since nothing makes it onto the screen except the datathere are no interpolative artifacts to bias the interpretation. 

Related Techniques 
Run Sequence Plot Box Plot Block Plot 

Case Study  The scatter plot is demonstrated in the load cell calibration data case study.  
Software  Scatter plots are a fundamental technique that should be available in any general purpose statistical software program. Scatter plots are also available in most graphics and spreadsheet programs as well. 