A unit root is a property of a non-stationary time series which can lead to spurious regressions and wrong inference.

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Best practice for ADF/KPSS unit root testing sequence?

I've been quite confused by the various unit root testing strategies recommended in the literature, so I was hoping others may have some advice on the best way to proceed using ADF and KPSS tests. ...
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13 views

Different results in ADF test

I have a question regarding the results I am getting from the augmented dickey fuller test for unit root. I am conducting the test in Eviews and I have the option to choose from intercept/trend and ...
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9 views

Unit Root Confirmed- How generate the new series with Diff, Trend,Intercept

I have a data series that became stationary at first difference and including both Trend and Intercept. I know how to generate a new variable using first differencing (Eviews) but how should I cater ...
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21 views

KPSS test in R interpretation

So in the R package tseries's kpss.test function, it seems I can specify whether the null hypothesis is trend stationary or level stationary(default). ...
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1answer
24 views

Structural-break unit-root test

My problem is the following: I have a model forecasting the sales of a certain brand. In period 4 a strike caused the sales to decrease. I want to know whether this strike has caused the sales to ...
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2answers
58 views

How to interpolate a variable with frequency of 5 years to annual data?

I have two time-series variables: each has 14 points with an interval of 5 years. The precise years are: ...
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61 views

How to read UNIT ROOT TEST results obtained from EVIEWS? I mean what values do we study to interpret our result?

Null Hypothesis: D(OIL_PRICES) has a unit root Exogenous: Constant Lag Length: 0 (Automatic - based on SIC, maxlag=22) ...
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34 views

Interpretation of results for unitroot test

Let's say I have a pure random walk: ...
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21 views

Unit root in shares

Suppose that dependent variable is a share of sth (for example it is a % of positive answers to the same question in each period of time t). If data shows the unit ...
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15 views

Unit Root Test and rolling data

Please could you kindly advise on the implication of testing for unit root (using the augmented dickey fuller approach) on rolling data. My feeling is that this wouldn't make much sense given the non ...
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73 views

Unit roots and GMM estimation

I want to estimate panel models of the following structure: $y_{it} = \rho y_{i,t-1} + \beta_1 x_1 + \dots + \beta_k x_k + c_i + \gamma_t + \epsilon_{it}$, where $c_i$ are time constant country ...
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43 views

Which type of random walk (1? 2? 3?) can unit root test?

Campbell (1997) showed that there are three types of random walk hypotheses classified by the level of restrictions on $\epsilon_t$: RW1 (random walk 1: increments are independent identically ...
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55 views

Time Series Econometrics: Cointegration methods for series with mixed degree of integration

I am performing a time series analysis on dataset ranging from 1974-2008. I have performed Augmented Dickey Fuller tests and Phillips Perron tests to check the stationarity/ order of integration of my ...
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321 views

Difference between series with drift and series with trend

A series with drift can be modeled as $y_t = c + \phi y_{t-1} + \epsilon_t$ where $c$ is the drift(constant), and $\phi=1$ A series with trend can be modeled as $y_t = c + \delta t + \phi y_{t-1} + ...
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382 views

Interpreting Augmented Dickey-Fuller in R

I know that this has been discussed before, but those discussions did not really answer my questions. I know how the ADF test works, but I am having trouble interpreting the output for the three ...
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45 views

Contradictory xtunitroot results

I am using unit root tests in Stata's xtunitroot command. The data are annual wage replacement rates for unemployment benefits in each of the 50 states for 1977 to 2006. (They vary noticably from ...
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39 views

Time series with an order of integration greater than 1

The issue of unit roots and what $ I(1) $ variables do to a regression estimation is covered clearly online. However, it is of course possible to have order of integration greater than 1. What does it ...
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1answer
180 views

How to conduct the Lluís Carrion-i-Silvestre et al. (2005) LM Unit Test and the non-linear ADF in Stata?

I am trying to test stationarity for a panel of 15 countries current account (1980–2012) annual data in Stata. I have chosen the LM unit root test by Lluís Carrion-i-Silvestre et al. (2005; to ...
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30 views

unit root testing for exogenous variables

I am running Cointegration and VECM on a set of endogenous and exogenous variables. Do I have to run unit root tests on the exogenous variables and make sure they are I(1)? Thanks a lot.
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3answers
482 views

Augmented Dickey Fuller output conflicting in Stata

I am required to perform unit root testing on a given time series. The output obtained in Stata is somewhat confusing me. To the best of my knowledge I am obtaining two conflicting results, Stata ...
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66 views

ADF-how to choose from the results?

I am a student and I have a project to do but I have some questions about ADF test. I have 52 observations of quarterly data. I have done the ADF test in my variables in the levels. I tested with ...
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16 views

Comparison test in unit root

I am not clear how to compare all the tests in Unit Root. Which one is the most powerful among: ADF PP KPSS Elliott, Rothenberg & Stock Unit Root Test
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29 views

Regression when you have both I(1) and I(2) processes

I want to estimate $\log Y_t=\beta_0+\beta_1\log X_{1t}+\beta_2\log X_{2t}+e_t$ Using ADF-tests, I have found that both $\{\log Y_t\}$ and $\{\log X_{1t}\}$ are I(1) (i.e. they contain a unit root), ...
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21 views

Can co-integration be conducted if one of the variables is not of the same order?

All my independent variables are stationary at their levels except one variable which became stationary after first difference i.e. my dependent variable. Can I still conduct co-integration test ?
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191 views

If time series is tested for Unit Root by ADF, PP, KPSS,… which one is preferred?

If time series is tested for Unit Root, (by ADF, PP, KPSS,...) problem is detected with some tests and not found by others. which one is preferred? For example if ADF says us that Unit root is existed ...
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79 views

Augmented Dickey-Fuller test

I am now working with Stata and I found out I have a unit root in my regression. How can I correct for this, because I can read everywhere what the test does but if you have a unit root, what to do ...
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117 views
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100 views

Cointegrated series

My problem is this: I have 2 series $y$ and $x$ that I want to verify are cointegrated. So first I verified them with ADF unit root test and revealed that one variable is integrated at first ...
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297 views

Confusion about the term “stochastic drift”

After reading lots of material about the subject, I believe that the term "stochastic drift" is defined in a two different ways. These two different definitions make the term unambiguous and I assume ...
2
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1answer
95 views

prove that this expression converges in probability to zero

Apparently $T^{-3/2} \sum\limits_{t=1}^T{y_{t-1}}u_t$ converges by law to $0.5\times T^{-1/2}\sigma^2 (X-1)$, where $X$ is a $\chi^2(1)$ random variable. $u_t$ is white noise and $y_t$ is an AR(1) ...
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196 views

What is the best way to proof your time series has a deterministic linear trend

In case you suspect your time series has a linear trend, what is the best way to prove it? If you just regress it against time, you ignore the auto correlation of the time series so I assume that is a ...
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219 views

Raw Prices vs. Daily Return vs. Price Ratio - ADF unit-root test

As the title suggests, I'd like to ask what the difference between using Raw Prices vs. Daily Return vs. Price Ratio in the Augmented Dickey-Fuller unit-root test. The context is that I am trying to ...
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2answers
72 views

Alternatives to Dickey-Fuller test

I'm studying unit root tests and therefore the Dickey Fuller test and I can't seem to figure the following out. Is it correctly understood that the Dickey Fuller test (with drift and constant) is ...
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26 views

Distribution of deterministic terms when process is non-stationary (integrated of order I(1), has a unit root)

I am looking for literature (or a solution if there is an easy one) on the asymptotic distribution of deterministic terms in linear regression models when the process is unit-root non-stationary I(1). ...
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104 views
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127 views

Paneldata regression where some variables have common unit roots

I've got paneldata on Y, A, B, C. And I am trying to model dependent variable Y on independent variables A, B, C. First I checked for unit roots (in Eviews). Y, A, B, C have no individual unit ...
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1answer
229 views

Dynamic Panel models, GMM, Stata

I am writing a paper about the contribution of foreign banks to economic growth (real GDP per capita), using a panel dataset for $N=6$ countries and $T=40$ quarters. I was planning to use GMM, but I ...
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63 views

Statistical power of unit root test

When studying time series, I once heard the statement that unit root test is less powerful. I hereby have two questions: What does it mean for a test to be powerful? What causes the unit root ...
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47 views

Test of stationarity in Dickey and Fuller test

Why is that in DF (Dickey and Fuller) test, the test verifies that $Tst = 0$ or $Tst < 0$. Why not test $\Phi = 1$ or $\Phi < 1$? Need some guidance on this
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2answers
180 views

About the stationarity of a sine wave

I generated two sine wave time series and want to check the stationarity of them. (1) The first time series is short. kpss.test() thinks it is stationary. ...
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1answer
116 views

What is the real meaning of null hypothesis in unit-root test for a AR(p) process?

There are functions in R (e.g., PP.test and adf.test) which have null hypothesis of unit-root in the process ($H_0$: there is a ...
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1answer
110 views

How to explain this unit root process?

I have a time series $X_t$ (shown below) with a structure break. The stationary test kpss.test() says it has a unit root. How to explain this? Why does $X_t$ have a ...
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784 views

Unit root tests: how to decide if to include a trend and/or a constant

Applying a test to univariate time series data for checking if the series has a unit root or not, one is faced with a decision if one would like to test if the series is stationary around a constant ...
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82 views

Is this a stationary time series?

I have a wait-time time series for 10 weekdays(2 weeks) with 10 minutes intervals. I'm having hard time to interpret this? Is this stationary? I also applied Philips-Perron Unit root test and I got ...
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3k views
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254 views

Exogenous regressors in panel unit root test

From visual inspection I suspect some of the series in my panel dataset to be non-stationary. If I do the panel unit root test on them in EViews 7, I can choose exogenous regressors under ...
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1answer
445 views

How to interpret the result of Fisher's unit root test [duplicate]

Following are the results from Fisher-type unit-root test for RDI (dependent variable). How do you interpret it? ...
0
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1answer
57 views

Testing for a root larger than 1 in AR(p)

My question is the following: How to test for a root larger than 1 in AR(p) process from its observations. Thanks in advance.
4
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3k views

Fisher-type unit-root test for panel data. Results interpretation in Stata

As part of my master thesis, I'm performing several tests on panel data. One of these is a Fisher-type unit-root test, which works well with an unbalanced panel. I have performed the test, but I ...
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1answer
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Connection of t-statistic and p-value in augmented Dickey-Fuller test

My project is about purchasing power parity (PPP). I am checking whether the real exchange rate of Canadian dollar(CAD)/US dollar(USD), Japanese Yen(JPY)/USD and Great Britain Pound(GBP)/USD has a ...