1.
Exploratory Data Analysis
1.3. EDA Techniques 1.3.3. Graphical Techniques: Alphabetic 1.3.3.26. Scatter Plot


Scatter Plot Showing Quadratic Relationship  
Discussion 
Note in the plot above how no imaginable simple straight line
could ever adequately describe the relationship between X
and Ya curved (or curvilinear, or nonlinear) function
is needed. The simplest such curvilinear function is a quadratic
model
