People attach great importance to knowing “the facts”. And figures have a special significance for many. But they are also easy to misread, to misunderstand and to manipulate. That's why you sometimes hear the phrase “lies, damned lies and statistics” (first coined by Benjamin Disraeli, Prime Minister of England in the late 1800s).

This chapter sets out particular areas where journalists need to take extra care. It is easy to stumble if you are not careful. Knowing about percentage errors, means, averages, medians, modes and standard deviations, for instance, could be vital if you are to report meaningfully. Understanding polls might also be critical. A knowledge of spreadsheets will allow you to read other people's and help you construct your own.

This chapter can't show you everything you need to know, any more than the chapter on grammar gave you a complete course in English grammar. What follows are examples of situations where mistakes all too easily arise, with explanations of how to avoid those mistakes.

Percentage error

A change in the rate of inflation from 2% to 3% is not a 1% rise in inflation. It is a 50% rise. A rise from 2% to 3% is a one percentage point change. And a percentage change to a base figure to produce a new figure cannot be reversed back to the original base by applying an equal percentage change to the new figure in the opposite direction.