Benford’s Law

The surprising first digit

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Benford's law: first digit $d$ appears with probability $\log_{10}(1 + 1/d)$.
• About 30% of such numbers start with 1, under 5% with 9.
• It holds for data spanning many orders of magnitude, and helps detect fabricated numbers.

Steps

1. A guess
2. Powers of two
3. Around the log circle
4. Digit one
5. Change the units
6. Catching fraudsters
7. Digits 1 to 3