3.2. Probability Distribution http://www.ck12.org
We can add a sixth column to the table above to show the probability of each of these events (the 3 spins of the
spinner).
TABLE3.8:
Trial First Spin Second Spin Third Spin X P(X)1 R R R (^318)
2 R R B (^218)
3 R B R (^218)
4 R B B (^118)
5 B R R (^218)
6 B B R (^118)
7 B R B (^118)
8 B B B (^018)
As you can see in the table, each event has an equally likely chance of occurring. You can see this by looking at
the columnP(X). From here, we can find the probability distribution. In theXcolumn, we have 4 possible discrete
values for this variable: 0, 1, 2, and 3.
P( 0 ) =trial 8=
1
8
P( 1 ) =trial 4+trial 6+trial 7=1
8
+
1
8
+
1
8
=
3
8
P( 2 ) =trial 2+trial 3+trial 5=1
8
+
1
8
+
1
8
=
3
8
P( 3 ) =trial 1=1
8
Practice
- Does the following table represent the probability distribution for a discrete random variable?
X 2 4 6 8
P(X) 0. 2 0. 4 0. 6 0. 8- Does the following table represent the probability distribution for a discrete random variable?
X 1 2 3 4 5
P(X) 0. 202 0. 174 0. 096 0. 078 0. 055- Does the following table represent the probability distribution for a discrete random variable?
X 1 2 3 4 5 6
P(X) 0. 302 0. 251 0. 174 0. 109 0. 097 0. 067