algebra

in algebra numbers are represented as letters and other symbols when giving equations or formulae. Algebra therefore is the basis of statistical equations. So a typical example is the formula for the mean:

In this m stands for the numerical value of the mean, X is the numerical value of a score,

N is the number of scores and Σ is the symbol indicating in this case that all of the scores under consideration should be added together.

One difficulty in statistics is that there is a degree of inconsistency in the use of the symbols for different things. So generally speaking, if a formula is used it is important to indicate what you mean by the letters in a separate key.