34.1 Introduction
In probability theory an event is either independent or dependent. This chapter
describes the
differences and how each type of event is worked with.
34.2 Definitions
Two events are independent if knowing something about the value of one event
does not give
any information about the value of the second event. For example, the event of
getting a ”1”
when a die is rolled and the event of getting a ”1” the second time it is thrown
are independent.

Definition: Independent Events
Two events A and B are independent if when one of them happens, it
doesn’t affect the
other one happening or not. 
The probability of two independent events occurring, P(A ∩
B), is given by:
Consequently, two events are dependent if the outcome of
the first event affects the outcome of
the second event.
34.2.1 Identification of Independent and Dependent Events
Use of a Contingency Table
A twoway contingency table (studied in an earlier grade) can be used to
determine whether
events are independent or dependent.

Definition: twoway contingency table
A twoway contingency table is used to represent possible outcomes when
two events are
combined in a statistical analysis. 
For example we can draw and analyse a twoway contingency
table to solve the following problem.