Unit root
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In autoregressive models in econometrics a unit root is present if the coefficient | b | = 1 in 
, where − yt is the variable of interest at time t, b is the slope coefficient, and 
is the error component.
If the unit root is present, the time series is said to have a stochastic trend, or being integrated of order one or I(1).
[edit] See also
- Dickey-Fuller test
- Phillips-Perron test
