Granger Causality Test
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Granger causality From Wikipedia, the free encyclopedia The Granger causality test is a statistical hypothesis test for determining whether one time series is useful in forecasting another. [1] Ordinarily, regressions reflect "mere" correlations, but Clive Granger, who won a Nobel Prize in Economics, argued that there is an interpretation of a set of tests as revealing something about causality. A time series X is said to Granger-cause Y if it can be shown, usually through a series of t-tests and F-tests on lagged values of X (and with lagged values of Y also included), that those X values provide statistically significant information about future values of Y. Method If a time series is stationary, the test is performed using the level values of two (or more) variables. If the variables are non-stationary, then the test is done using first (or higher) differences. The number of lags to be included is usually chosen using an information criterium, such as the Akaike information criterion or the Schwarz information criterion. Any particular lagged value of one of the variables is retained in the regression if (1) it is significant according to a t-test, and (2) it and the other lagged values of the variable jointly add explanatory power to the model according to an F-test. Then the null hypothesis of no Granger causality is not rejected if and only if no lagged values of an explanatory variable have been retained in the regression. In practice it may be found that neither variable Granger-causes the other, or that each of the two variables Granger-causes the other. Limitations As its name implies, Granger causality is not necessarily true causality. If both X and Y are driven by a common third process with different lags, one might still accept the alternative hypothesis of Granger causality. Yet, manipulation of one of the variables would not change the other. Indeed, the Granger test is designed to handle pairs of variables, and may produce misleading results when the true relationship involves three or more variables. A similar test involving more variables can be applied with vector autoregression. Mathematical statement Let y and x be stationary time series. To test the null hypothesis that x does not Granger-cause y, one first finds the proper lagged Granger causality - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Granger_causality 1 of 3 08/02/2013 5:42 PM
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Test for Granger Causality
Transcript of Granger Causality Test
Granger causalityFrom Wikipedia, the free encyclopedia
The Granger causality test is a statistical hypothesis test for determining whether one time series is useful in forecasting another.[1]
Ordinarily, regressions reflect "mere" correlations, but Clive Granger, who won a Nobel Prize in Economics, argued that there is aninterpretation of a set of tests as revealing something about causality.
A time series X is said to Granger-cause Y if it can be shown, usually through a series of t-tests and F-tests on lagged values of X (andwith lagged values of Y also included), that those X values provide statistically significant information about future values of Y.
MethodIf a time series is stationary, the test is performed using the level values of two (or more) variables. If the variables are non-stationary,then the test is done using first (or higher) differences. The number of lags to be included is usually chosen using an informationcriterium, such as the Akaike information criterion or the Schwarz information criterion. Any particular lagged value of one of the variablesis retained in the regression if (1) it is significant according to a t-test, and (2) it and the other lagged values of the variable jointly addexplanatory power to the model according to an F-test. Then the null hypothesis of no Granger causality is not rejected if and only if nolagged values of an explanatory variable have been retained in the regression.
In practice it may be found that neither variable Granger-causes the other, or that each of the two variables Granger-causes the other.
LimitationsAs its name implies, Granger causality is not necessarily true causality. If both X and Y are driven by a common third process withdifferent lags, one might still accept the alternative hypothesis of Granger causality. Yet, manipulation of one of the variables would notchange the other. Indeed, the Granger test is designed to handle pairs of variables, and may produce misleading results when the truerelationship involves three or more variables. A similar test involving more variables can be applied with vector autoregression.
Mathematical statementLet y and x be stationary time series. To test the null hypothesis that x does not Granger-cause y, one first finds the proper lagged
Granger causality - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Granger_causality
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values of y to include in a univariate autoregression of y:
Next, the autoregression is augmented by including lagged values of x:
One retains in this regression all lagged values of x that are individually significant according to their t-statistics, provided that collectivelythey add explanatory power to the regression according to an F-test (whose null hypothesis is no explanatory power jointly added by thex's). In the notation of the above augmented regression, p is the shortest, and q is the longest, lag length for which the lagged value of xis significant.
The null hypothesis that x does not Granger-cause y is accepted if and only if no lagged values of x are retained in the regression.
ExtensionsA method for Granger causality has been developed that is not sensitive to deviations from the assumption that the error term is normallydistributed.[2] This method is especially useful in financial economics since many financial variables are non-normally distributed.[3]
Recently, asymmetric causality testing has been suggested in the literature in order to separate the causal impact of positive changesfrom the negative ones.[4]
References^ Granger, C. W. J. (1969). "Investigating Causal Relations by Econometric Models and Cross-spectral Methods". Econometrica 37 (3): 424–438.doi:10.2307/1912791 (http://dx.doi.org/10.2307%2F1912791) . JSTOR 1912791 (http://www.jstor.org/stable/1912791) .
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^ Hacker R.S. and Hatemi-J A. (2006) "Tests for causality between integrated variables using asymptotic and bootstrap distributions: theory andapplication" (http://ideas.repec.org/a/taf/applec/v38y2006i13p1489-1500.html) , Applied Economics, Vol. 38(13), pp. 1489–1500.
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^ Mandelbrot, Benoit (1963). "The variation of certain speculative prices". Journal of Business 36 (1): 394–419.3.^ Hatemi-J, A. (2012). "Asymmetric causality tests with an application". Empirical Economics 42 (6): forthcoming. doi:10.1007/s00181-011-0484-x(http://dx.doi.org/10.1007%2Fs00181-011-0484-x) .
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Granger causality - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Granger_causality
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Further reading
Seth, Anil (2007). "Granger causality". Scholarpedia 2 (7): 1667. doi:10.4249/scholarpedia.1667 (http://dx.doi.org/10.4249%2Fscholarpedia.1667) .
See alsoConvergent cross mapping
Econometrics
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