Z-score move
How many standard deviations a price move is from its recent typical move, used to flag unusual moves.
A z-score measures a move against normal behavior. Take the period's percent change, subtract the average of recent changes, and divide by their standard deviation. A z-score near 0 is an ordinary move. A z-score of 3 or more is rare under a normal distribution, although assets with fat tails produce such moves more often than a bell curve suggests.
On our site, a z-score move is shown next to flagged price changes and is computed over a stated lookback window. A high score means the move was unusual for that asset, not that it was large in absolute terms.
Traders care because a 3 percent move in a utility and a 3 percent move in a crypto token mean very different things. The z-score puts both on one scale.
Worked example (illustrative numbers, not real data): an asset's recent daily moves average 0.2 percent with a standard deviation of 1.0 percent. Today it moves 3.2 percent. The z-score is (3.2 - 0.2) / 1.0 = 3.0, which we would flag as unusual.