A Venn diagram is a picture that represents the outcomes of an experiment. It generally consists of a box together with circles or ovals. The circles or ovals represent events.
Suppose an experiment has the outcomes 1, 2, 3, ... , 12 where each outcome has an equal chance of occurring. Let event A =
{1, 2, 3, 4, 5, 6}A =
{1, 2, 3, 4, 5, 6}
and event A =
{6, 7, 8, 9}A =
{6, 7, 8, 9}. Then A AND B =
{6}A AND B =
{6} and A OR B =
{1, 2, 3, 4, 5, 6, 7, 8, 9}A OR B =
{1, 2, 3, 4, 5, 6, 7, 8, 9}. The Venn diagram is as follows:

Flip 2 fair coins. Let AA = tails on the first coin. Let BB = tails on the second coin. Then A = {TT, TH} A={TT,TH} and B = {TT, HT}B={TT,HT}.
Therefore, A AND B = {TT}A AND B = {TT}.
A OR B = {TH, TT, HT}A OR B = {TH,TT,HT}.
The sample space when you flip two fair coins is S = {HH, HT, TH, TT}S ={HH,HT, TH,TT}. The outcome HHHH is in neither AA nor BB. The Venn diagram is as follows:

Forty percent of the students at a local college belong to a club and 50% work part time. Five percent of the students work part time and belong to a club. Draw a Venn diagram showing the relationships. Let CC = student belongs to a club and PT PT = student works part time.

- The probability that a students belongs to a club is P(C) = 0.40P(C)= 0.40.
- The probability that a student works part time is P(PT) = 0.50P(PT)=0.50.
- The probability that a student belongs to a club AND works part time is P(C AND PT) = 0.05P(C AND PT)= 0.05.
- The probability that a student belongs to a club given that the student works part time is:
P(C|PT)
=
P(C AND PT)
P(PT)
=
0.05
0.50
=
0.1
P(C|PT) =
P(C AND PT)
P(PT)
=
0.05
0.50
= 0.1
(1)
- The probability that a student belongs to a club OR works part time is:
P(C OR PT)
=
P(C)
+
P(PT)
-
P(C AND PT)
=
0.40
+
0.50
-
0.05
=
0.85
P(C OR PT) = P(C) + P(PT) - P(C AND PT) = 0.40 + 0.50 - 0.05 = 0.85
(2)
- Venn Diagram:
The useful visual representation of a sample space and events in the form of circles or ovals showing their intersections.
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