How to Lie with Statistics
By Darrell Huff (1954)
If I purchase an article every morning for 99 cents and sell it each afternoon for one dollar, I will make only 1 per cent on total sales, but 365 per cent on invested money during the year.
Be very careful about the conclusions reached:
- Who says so?
- How does he or she know?
- What’s missing?
- Does it make sense?
When talking about percentiles, if the distribution is normal, those in the middle are much more similar than those at the extremes. 90 to 90% is a bigger difference than 50 to 60%.
Percentages don’t add. If rent goes up 10% and utilities go up 10%, the total increase isn’t 20%.