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MATHEMATICS
Since we had assumed that each family is equally likely to be selected, the probability
that family f4 is selected is 1
10 Thus, the probability that X can take the value 2 is 1
10 We write P(X = 2) = 1
10
Also, the probability that any one of the families f1, f3 or f7 is selected is
P({f1, f3, f7}) = 3
10
Thus, the probability that X can take the value 3 = 3
10
We write
P(X = 3) = 3
10
Similarly, we obtain
P(X = 4) = P({f2, f6, f9}) = 3
10
P(X = 5) = P({f5, f10}) = 2
10
and
P(X = 6) = P({f8}) = 1
10
Such a description giving the values of the random variable along with the
corresponding probabilities is called the probability distribution of the random
variable X In general, the probability distribution of a random variable X is defined as follows:
Definition 5 The probability distribution of a random variable X is the system of numbers
X
:
x1
x2