Random walk
A model in which the next change of price does not depend on the changes before it.
How to read the number
The model is needed as a baseline: series generated from it display trends, levels and familiar shapes. Their mere presence therefore proves nothing.
When the metric lies
It does not follow from the model that markets are random. What follows is narrower: a discovered regularity must be compared with a random series before it may be called a regularity.
Also known as: random walk hypothesis