Economictrics

Phillips-Perron (PP) Unit Root Tests The shirtfront chockablock(predicate) turn out involves enough the regression model ?yt = ?yt?1 + (constant, time trend) + ut (1) by ordinary least squargons (OLS), precisely consecutive coefficient of correlativity go forth present a problem. To account for this, the augmented impair chock- honest examines regression includes cast outs of the frontmost differences of yt. The Phillips Perron test involves commensurate (1), and the results are used to calculate the test statistics. They estimate non (1) but: yt = ?yt?1 + (constant, time trend) + ut (2) In (1) ut is I(0) and may be heteroskedastic. The PP tests correct for any serial correlation and heteroskedasticity in the errors ut non-parametrically by modifying the Dickey Fuller test statistics. Phillips and Perrons test statistics can be viewed as DickeyFuller statistics that have been made big-shouldered to serial correlation by using the NeweyWest (1987) heteroskedast icity- and autocorrelation-consistent covariance matrix calculator. down the stairs the unavailing system that ? = 0, the PP Zt and Z? statistics have the same asymptotic statistical distributions as the ADF t-statistic and normalized diagonal statistics. One good of the PP tests over the ADF tests is that the PP tests are robust to general forms of heteroskedasticity in the error term ut.

another(prenominal) advantage is that the user does not have to specify a lag length for the test regression. We have not dealt with it, but the Dickey Fuller test produces two test statistics. The normalized bias T (?? 1) has a well defined limiting distribution that does not depend on nuisance par ameters it can likewise be used as a test s! tatistic for the cryptograph hypothesis H0 : ? = 1. This is the second test from DF and relats to Z? in Phillips and Perron. Continued...............  evoke FROM STATA MANUAL mention the regression is y on lagged y, not differenced y on lagged y. ZT is the ad skillfuled t statistic as in Dickey Fuller. is just the equivalent in tthe t stat in the DF test. S2n is an unbiased estimator (OLS) of the variance...If you want to get a full essay, order it on our website: OrderEssay.net

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