Asking the Right Questions, A Guide to Critical Thinking, 8th Ed

156 Chapter 11
that people can "lie with statistics." However, this chapter will provide some
general strategies that you can use to detect such deception. In addition, it will
alert you to flaws in statistical reasoning by illustrating a number of the most
common ways that authors misuse statistical evidence.
(j) Critical Question: Are the statistics deceptive?
Unknowable and Biased Statistics
The first strategy for locating deceptive statistics is to try to find out as much
as you can about how the statistics were obtained. Can we know precisely the
number of people in the United States who cheat on their taxes, have premarital
sex, drink and drive, run red lights, use illegal drugs, hit a car in a
parking lot and left without informing anyone, buy pornographic material,
fail to rewind a video before returning it to the video store, or illegally download
music? We suspect not. Why? Because there are a variety of obstacles
to getting accurate statistics for certain purposes, including unwillingness to
provide truthful information, failure to report events, and physical barriers to
observing events. Consequently, statistics are often in the form of "educated
guesses." Such estimates can be quite useful; they can also be quite deceiving.
Always ask, "How did the author arrive at the estimate?"
Confusing Averages
Examine the following statements:
(1) One way to make money fast is to become a professional golfer. The average
professional golfer made $874,840.23 in tournament earnings alone in 2004.
(2) There is no reason to worry about the new nuclear power plant's being built
in our city; the average amount of harm caused by nuclear accidents is rather low.
Both examples use the word "average." But there are three different ways to
determine an average, and in most cases each will give you a different average.
What are the three ways? One is to add all the values and divide this total by the
number of values used. The result is the mean.
A second way is to list all the values from highest to lowest, then find the
one in the middle. This middle value is the median. Half of the values will be
above the median; half will be below it. A third way is to list all the values and