Be Skeptical of Averages
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Be Skeptical of Averages

Lessons from A Field Guide to Lies.

An average is a helpful summary statistic to help us characterise a large amount of information with a single number.

Averages are often used to express outcomes. But in reality, averages are manipulated by the authorities, companies, and those in power to fool you.

The pitfalls of drawing conclusions about individuals and groups based on averages are common, they are known as ecological fallacy and the exception fallacy.

An ecological fallacy occurs when you make inferences about an individual based on aggregate data.

An exception fallacy occurs when you make inferences about a group based on knowledge of a few exceptional individuals, the outliers.

You have to be careful of averages and how they’re applied. One way that they can fool you is if the average combines samples from disparate populations. Remember that the average doesn’t tell you anything about the range.