271 / 762
Chapter 7: Probability
271
Figure 7-2:
Tree diagram for a three-child family
From
Figure 7-2
, if you follow along the “branches” of the tree, you will
trace out all the possible outcomes as listed on the right hand side. Thus, the
sample space is then
S
= {
BBB, BBG, BGB, BGG, GBB, GBG, GGB, GGG
}.
Events
Sometimes we may only be interested in part of the sample space.
For example, we may only be concerned with one girl in a three-child
family; that is, the outcomes of
BBG
and
BGB
. These two outcomes
constitute a subset of the sample space. Such subsets are called
events
.