CUSUM Test
The CUSUM or Cumulative Sum test is a statistical quality control technique used in financial markets to detect small, persistent shifts in the mean of a time series. In the context of cryptocurrency and derivatives, it is employed to monitor price data or order flow for structural breaks that might indicate a change in market regime, such as the onset of a new trend or a shift in volatility.
The test works by accumulating the deviations of observations from a target mean over time. When the cumulative sum exceeds a predefined threshold, it signals that the underlying process has deviated significantly from its expected behavior.
Traders and risk managers use this to identify early warning signs of market manipulation, flash crashes, or sudden liquidity drying up. Unlike simple moving averages that react to the most recent data, CUSUM is highly sensitive to the persistence of deviations, making it effective for identifying subtle shifts before they become obvious to the broader market.
It is a critical tool in quantitative finance for maintaining the integrity of automated trading strategies and risk monitoring systems.