Statistical Notation Refresher

In the course of validating or developing a model you may come across (or even write your own) statistical notation.  Understanding the notation and using it correctly helps in interpreting model formulas.  I find it helpful to have a guide to remind me of what the symbols mean.  It also helps for me to remember that statistical notation really is just trying to simplify or more complex and involved series of steps to get to an end result.  Here are notations I have come across:

r (delta):   Change

Subscript t :  At time t (where t can vary), example:

Subscript t-1 (example:  ):  At time t-1 (lagged), example:

 

β (beta):  Sign used to represent a coefficient of an independent variable

 

exp:  It means you take the exponential, example: 

Subscript small i (as shown above):   observation i of many

 

ε (epsilon):  Denotes the error in a statistical equation

 

u:  (upsilon):  Also denotes the error (variance)

 

S :  Summation

 

P:  Product symbol

 

g (Gamma):   

 

a (Alpha): 

 

|:  Used for conditional probability, example: