STATISTICS AND PROBABILITY
LESSON 2 – PROBABILITY DISTRIBUTION OF THE DISCRETE RANDOM
VARIABLE
DISCRETE RANDOM VARIABLE
A discrete random variable is one that can assume only a
countable number of values.
PROBABILITY DISTRIBUTION
It is a listing of the possible values and the corresponding probabilities
of a discrete random variable or a formula for the probabilities.
Example 1.
A basket contains 10 ripe and 4 unripe bananas. If three bananas are taken
from the basket one after the other, determine the possible values of the
random variable R representing the number of ripe bananas. Construct the
probability distribution of the random variable R.
Step 1. List the sample space of this experiment. Let R represent the ripe
bananas and let U represent the unripe bananas
S = {RRR, RRU, RUR, URR, UUR, URU, RUU, UUU}
Step 2. Count the number of ripe bananas (R) in each outcome and assign
this number to this outcome.
OUTCOMES Number of Ripe
Bananas
(Value of R)
RRR 3
RRU 2
RUR 2
URR 2
UUR 1
URU 1
RUU 1
UUU 0
