Probability and Counting Rules
Would You Bet Your Life?
Humans not only bet money when they gamble, but also bet their lives by engaging in
unhealthy activities such as smoking, drinking, using drugs, and exceeding the speed
limit when driving. Many people don’t care about the risks involved in these activities
since they do not understand the concepts of probability. On the other hand, people may
fear activities that involve little risk to health or life because these activities have been
sensationalized by the press and media.
In his book
Probabilities in Everyday Life
(Ivy Books, p. 191), John D. McGervey
When people have been asked to estimate the frequency of death from various causes, the
most overestimated categories are those involving pregnancy, tornadoes, Foods, ±re, and
homicide. The most underestimated categories include deaths from diseases such as
diabetes, strokes, tuberculosis, asthma, and stomach cancer (although cancer in general is
The question then is, Would you feel safer if you Few across the United States on a
commercial airline or if you drove? How much greater is the risk of one way to travel
over the other? See Statistics Today—Revisited at the end of the chapter for the answer.
In this chapter, you will learn about probability—its meaning, how it is computed,
and how to evaluate it in terms of the likelihood of an event actually happening.
A cynical person once said, “The only two sure things are death and taxes.” This philos-
ophy no doubt arose because so much in people’s lives is affected by chance. ±rom the
time a person awakes until he or she goes to bed, that person makes decisions regarding
the possible events that are governed at least in part by chance. ±or example, should I
carry an umbrella to work today? Will my car battery last until spring? Should I accept
that new job?