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3 · Practitioner
Numbers That Lie
Numbers look objective, which is exactly why they are so easy to misuse – often without a single false figure. In this course you will learn to recognise the most common tricks: percentages without a baseline, truncated chart axes, averages distorted by extremes, correlations passed off as causes, and surveys that asked the wrong people. You do not need advanced maths, just basic arithmetic and a willingness to ask questions. All the figures in the examples are invented so that they are easy to work with.
5 lessonsabout 96 minutesquizzes and interactive gamesFree · after sign-up
Course contents
- 1Relative vs absolute risk, and percentages of percentagesWhy a “50% lower risk” can mean almost nothing, and why a price rise and a discount of the same percentage do not cancel out.18 min
- 2Misleading chartsTruncated axes, cherry-picked time periods, 3D effects and pictures instead of bars: how a chart can show something other than what the data say.18 min
- 3Mean, median and the “average person”When an average describes a typical value and when it distorts it – and why the average person does not actually exist.18 min
- 4Correlation is not causationWhen two things go hand in hand, it does not mean one causes the other. Hidden variables, reverse causation and chance.20 min
- 5Surveys and samplesWho asked whom, and how: selection bias, leading questions, survivorship and the margin of error.22 min