השוואת שיטות

	מבחן שורש יחידה פיליפס-פררון (PP)	מבחן שורש יחידה מורחב של דיקי-פולר (ADF)	מבחן קואינטגרציה (יוהנסן / אנגל-גריינג'ר)
תחום	אקונומטריקה	אקונומטריקה	אקונומטריקה
משפחה	Regression model	Regression model	Regression model
שנת המקור	1988	1979	1988
הוגה השיטה	Peter C. B. Phillips & Pierre Perron	David A. Dickey & Wayne A. Fuller	Engle & Granger (1987); Johansen (1988)
סוג	Unit-root test for stationarity	Unit-root test for stationarity	Time-series cointegration test
מקור מכונן	Phillips, P. C. B., & Perron, P. (1988). Testing for a unit root in time series regression. Biometrika, 75(2), 335–346.	Dickey, D. A., & Fuller, W. A. (1979). Distribution of the estimators for autoregressive time series with a unit root. Journal of the American Statistical Association, 74(366a), 427–431.	Johansen, S. (1988). Statistical Analysis of Cointegration Vectors. Journal of Economic Dynamics and Control, 12(2-3), 231-254.
כינויים	PP test, Phillips-Perron unit root test, Phillips-Perron birim kök testi	ADF test, Dickey-Fuller test, unit root test, Genişletilmiş Dickey-Fuller testi	Johansen cointegration test, Engle-Granger cointegration test, long-run equilibrium test, Eşbütünleşme Testi (Johansen/Engle-Granger)
קשורות	4	4	5
תקציר	The Phillips-Perron test, proposed by Peter Phillips and Pierre Perron in 1988, tests for a unit root in a time series, like the Augmented Dickey-Fuller test, but corrects for autocorrelation and heteroskedasticity in the errors non-parametrically rather than by adding lagged differences. It runs a simple Dickey-Fuller regression and then adjusts the test statistic using a long-run variance estimate, so the practitioner need not choose a lag length for the regression itself.	The Augmented Dickey-Fuller (ADF) test is the most widely used test for a unit root — that is, for whether a time series is non-stationary and must be differenced before modelling. Introduced by David Dickey and Wayne Fuller in 1979 and extended by Said and Dickey in 1984 to series with higher-order autocorrelation, it regresses the change in the series on its lagged level plus lagged differences and asks whether the lagged-level coefficient is zero.	The cointegration test examines whether non-stationary time series that each contain a unit root share a stable long-run equilibrium relationship. The single-equation residual approach was introduced by Engle and Granger (1987) and the system-based rank approach by Johansen (1988).