The suspicious-looking streak
Flip a coin twenty times and you may see five heads in a row. To a human, that feels suspicious. To probability, it is normal. Randomness does not promise alternation. In fact, genuinely random sequences often contain clusters, streaks and ugly little patterns.
This is why people can look at a chart of noisy data and feel that something meaningful is happening. A few points rise, a few points fall, and suddenly the mind writes a story.
The pattern machine
Pattern-finding is useful. It helps us learn language, spot danger and recognise faces. But it also makes us vulnerable to over-interpreting small samples. Statistics gives us a brake pedal: how surprising would this pattern be if nothing special was happening?
The practical lesson
Before explaining a short-run movement, ask whether the movement is larger than ordinary noise. If the answer is unclear, simulate. Simulation is often the fastest way to develop honest intuition.