## Frequency Function

When an outcome is a numerical value, the outcome determined by an experiment is referred as random variable (r.v.). We conventionally denote random variables by uppercase letters from the end of the alphabet. Particularly if the random variable takes ``discrete'' values such as 1,2,3, (or 0,1,2,3,), we call it a discrete random variable. The statement such as ``'' is an event, and therefore, is associated to the probability . We can assign for all the possible values (or ), which will completely describe the ``probabilistic nature of the random variable '', that is, the probability distribution of . is often called a frequency function, and simply written by .

The frequency function is graphically presented. The bar graph may be able to indicate a particular outcome with the highest frequency, the existence of mode of the distribution of interest.

To find the probability of an event from the frequency function , it is important to determine the exact range of the random variable . Then it is computed as

Essential parameters of discrete distribution are the mean and the standard deviation . They are computed as follows.

;