| |
The first step is to
represent the problem by a decision tree. There are three key
symbols in a decision tree:
- A box represents
a decision node. Lines from the box denote the decision
alternatives (one line per decision alternative). The name of
the decision alternative goes above the line.
- A circle represents
a chance node. Lines from the circle denote the events
that could occur at the chance node. The name of the chance-driven
event goes above the line. The probability of the event goes
below the line. Since all probabilities at a chance node must
sum to 1.0, one event is labeled simply as #, to denote "1
- the sum of the probabilities of the other events."
- A horizontal rectangle
represents a terminal node. A terminal node represents
an outcome state, so there are no events that occur distal to
a terminal node. The value of the outcome appears in the rectangle.
Below is a very simple decision tree for medical versus surgical
treatment.
| Figure
2.3.1: Simple Decision Tree for Medical Versus Surgical
Treatment
|
|---|
|
|
|
Question
2.3.1
What is
the probability represented by the symbol #?
 | The
sum of the life expectancies (LE) of each outcome at the chance
node, divided by the number of outcomes at that chance node
|
 | 1
plus the sum of the probabilities of the other events at the
chance node |
 | 1
minus the sum of the probabilities of the other events at
the chance node |
|