Random sequences are read as patterned, because true randomness contains more streaks than people expect.
In 30 coin flips a run of five is more likely than not. Cancer-cluster investigations repeatedly find that geographic clumping is what randomness looks like at small sample sizes.
In practice
- Four customer complaints in one week from the same postcode prompts a regional investigation; over a year, some week and some postcode had to be first.
- A trader has six good months and is promoted; the sequence is well within what a coin would produce.
- Further reading
- Wikipedia
- Subject
- Decision-making & Reasoning
- Essay
- The catalogue of predictable errors