Extrapolations are useful, particularly in that form of soothsaying called forecasting trends. But in looking at the figures or charts made from them, it is necessary to remember one thing constantly: The trend-to-now may be a fact, but the future trend represents no more than an educated guess. Implicit in it is “everything else being equal” and “present trends continuing.” And somehow everything else refuses to remain equal, else life would be dull indeed.
The book gives straightforward examples of how statistics may be used to deceive. Although written in 1954, it is actual and relevant. The writing is fluid and can be simply understood even from some who is not astute in mathematics.
Each chapter presents a particular twist of facts through statistics, usually taking an example from a journal or an advert. Because it is assumed that people give more credibility to facts presented through figures (the more precise, the better), those figures are used to mislead and misinterpret what is really happening.
To mention just a few twists: sample biases (for example a conservative magazine asking readers who they think will win the presidency); inadequate sampling (only 3 or 9 cases); difference between mean and median (the block of apartments might have a different average salary if a very rich man moves in; this doesn’t mean you are richer, but the average goes up); statistical differences lower than than the statistical error presented as relevant differences (such as IQ tests); graphs with no axis measurements; small differences made great through graph manipulations; infographic manipulations (when the difference is, let’s say x2, but the two objects compared in the infographic have surfaces presented at square (x4)); semi-attached figures (when you prove a fact and associate a second one to the first, letting the second fact subtly draw its veracity from the proof of the first); difference between forecast and extrapolation; and many others.
Overall, this little book from Darell Huff is a great defense technique manual for a critical thinker and it is a particular good recommendation for honest journalists, wanting to get the facts from press releases.