Thinking and Deciding

354 DECISION ANALYSIS AND VALUES
Table 14.2: Abbreviated decision analysis for birth control
HIV STD Preg. Easy Sex TOTAL
prev. prev. prev. use pleas. UTIL.
Pill 0 0 94 80 100 207.2
Condom 99 99 84 0 90 305.7
Diaphr. 0 0 82 0 95 160.6
None 0 0 15 100 100 152.0
Abstain 100 100 100 100 0 270.0
WEIGHT 1.00 .50 .80 .40 1.00
chlamydia, genital herpes, and many others, most curable if caught in time. The
range here is from no protection to perfect protection, for mutually monogamous relationships.
Pregnancy prevention. 0 represents the certainty of getting pregnant. Other numbers
reflect failure rates per year when used correctly. Note that no option has 0 because
pregnancy is not a certainty even without birth control.
Easy use. 100 is nothing to do. 0 is as bad as putting on a condom or inserting a
diaphragm.
Sexual pleasure. This is present mainly because of abstention as an option, but some
methods may reduce pleasure for some people.
The weights are filled in, but they would vary from person to person. With the
weights assigned, condom use is the best, and abstention is second best. Obviously,
that is because the risk of AIDS and other STDs combined is more important than
having sex at all. This can be true even though the question of birth control might not
come up except for the attribute of preventing pregnancy. The “reason” for making
a decision in the first place need not be the main consideration in choosing among
the options at hand. One of the lessons we learn from this sort of analysis is that it is
misleading to think of “a purpose” or “a reason” as good guides to decision making.
Each decision affects many different goals, usually, whatever led us to think about it
in the first place.
Weights are based on judgments, and many different kinds of judgments have
been used. A relatively simple method begins with choosing the most important
attribute range and then comparing other ranges to that. To do this for yourself, ask
yourself which is more important, the difference between the top and bottom of one
range (as you have defined the top and bottom) or the difference between the top and
bottom of another. 5 In thinking about pregnancy, you might want to think about how
5 Another, more complex, approach is to make up a hypothetical decision, for example, between two
methods that were identical except that one was as good as abstention on preventing pregnancy (100) and
as bad as pills at preventing STDs (0), and the other was as good as abstention at preventing STDs (100)
and led to certain pregnancy (0). When you do this, it is important to realize that the two methods are