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,
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
which will completely describe
the ``probabilistic nature of the random variable
that is, the probability distribution
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.