1. Background and Motivation

# 1.3 Summation Convention

For those of you who were ripped off in your high school education, a brief review of an important symbolic convention is given here. This convention will be used in the formulae that you will need to use.

The capital Greek Sigma, , means sum or add. For example, suppose that you have 5 data sample values, represented abstractly by and , or more abstractly (using set notation) by:

, (or )

If you want to add the 5 values you would write:

or

Sometimes people get lazy and leave off the *limits* on the summation sign and write

where it is hopefully clear that is the *summation index* . We can also leave off the summation index and write

just to remind us that we need to add up a bunch of numbers generically represented by . This last convention is useful for us because whenever we need to deal with a sum in a formula, we will get that sum from adding up numbers in a table that we have constructed.