Source: Enders 2003:213
Example
We would like to perform unit roots for the ln_VAT
Step1: Perform ADF test using the most general structure and record statistic
i.e VAT has a unit root (random walk with drift and time trend)
i.e. VAT is stationary
In Eviews this is very easy since the unit root options are sufficient. The initial selection lag order ,k, should be determined as i.e. integer of . The alternative is to use the automatic lag selection criteria such as the Bayesian information criterion, Swartz information criterion, Akaike information criterion
Go to view/unit root test
ADF Test Statistic
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-0.349651
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1% Critical Value*
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-3.5572
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5% Critical Value
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-2.9167
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10% Critical Value
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-2.5958
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*MacKinnon critical values for rejection of hypothesis of a unit root.
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Augmented Dickey-Fuller Test Equation
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Dependent Variable: D(LN_VAT)
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Method: Least Squares
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Date: 11/13/09 Time: 16:50
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Sample(adjusted): 2002 2054
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Included observations: 53 after adjusting endpoints
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Variable
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Coefficient
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Std. Error
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t-Statistic
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Prob.
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LN_VAT(-1)
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-0.020222
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0.057835
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-0.349651
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0.7281
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D(LN_VAT(-1))
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-0.493401
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0.118000
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-4.181357
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0.0001
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C
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0.205849
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0.489533
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0.420501
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0.6759
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R-squared
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0.282226
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Mean dependent var
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0.019825
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Adjusted R-squared
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0.253516
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S.D. dependent var
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0.193443
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S.E. of regression
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0.167134
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Akaike info criterion
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-0.685106
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Sum squared resid
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1.396684
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Schwarz criterion
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-0.573580
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Log likelihood
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21.15531
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F-statistic
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9.829928
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Durbin-Watson stat
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2.091018
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Prob(F-statistic)
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0.000251
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Perform hypothesis test using the critical values from Eviews. Remember that the the ADF unit root test is left tail.
In our case we cannot reject the null of unit roots(Remember the ADF test is a left tail test).
In our case the computed ADF statistic is in the acceptance/fail to reject region. Thus we fail to reject the null hypothesis that money supply m3 has unit roots with drift and time trend.
Repeat the test
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