EXAMINATION OF SOME MORE POWERFUL MODIFICATIONS OF THE DICKEY- FULLER TEST

Although the t-ratio variant of the Dickey-Fuller test is the most commonly applied unit root test in practical applications, it has been known for some time that readily implementable, more powerful modifications are available. We explore the large sample properties of five of these modified tests, and the small sample properties of these five plus six hybrids. As a result of this study we recommend two particular test procedures.

Behaviour of Dickey-Fuller Unit Root Tests Under Trend Misspecification

We analyse the case where a unit root test is based on a Dickey-Fuller regression whose only deterministic term is a fixed intercept. Suppose, however, as could well be the case, that the actual data generating process includes a broken linear trend. It is shown theoretically, and verified empirically, that under the I(1) null and I(0) alternative hypotheses the Dickey-Fuller test can display a wide range of different characteristics depending on the nature and location of the break.

Statistics for Business and Economics -7/E.

A classic text for accuracy and statistical precision.Statistics for Business and Economics enables readers to conduct serious analysis of applied problems rather than running simple “canned” applications. This text is also at a mathematically higher level than most business statistics texts Provides readers with the knowledge they need to become stronger analysts for managerial positions. These include the following: 1. Increased number of real world examples derivedfrom current businesses and current events 2. Expanded discussion of variance, shape of a distribution, and the interquartile range 3. Improved readability based on real and relevant business concerns 4. Revised and improved discussion of probability, including further emphasis on conditional probability and bayes theorem, which are importhant for management decision making 5. Expanded portfolio analysis using new monthly stock price and stock return data for the post 2,000 time period 6. Portfolio methodology extending beyond two securities, which indicated the complexity and procedures for developing portfolio means and variances 7. Very strong and in depth development of linear regression 8. Extended discussion of multicollinearity with guidelines for adjustment 9. Estimation of financial beta coefficients and their interpretation 10. Application of dummy variable models to public sector policy analysis 11. Improved discussion of finite population sampling and confidence intervals 12. Increased applications in finance, accounting, and marketing 13. Expanded discussion of categorical data analysis with marketing application

Properties of macroeconomic forecast errors

This paper investigates the distributional properties of individual and consensus time series macroeconomic forecast errors, using data from the Survey of Professional Forecasters. The degree of autocorrelation and the presence of ARCH in the consensus errors is also determined. We find strong evidence of leptokurtic forecast errors and some evidence of skewness, suggesting that an assumption of error normality is inappropriate; many of the forecast error series are found to have non-zero mean, and we find sporadic evidence of consensus error ARCH. Properties of the distribution of cross-sectional forecast errors are also examined

Forecasting daily cash receipts and disbursements : a general statistical approach

Includes bibliographical references (p. 21-22)

Profiles of cash flow components

Includes bibliographical references (p. 20-22)

Seasonal unit root tests with seasonal mean shifts

This paper analyses additive outlier and innovational outlier tests for seasonal unit roots when seasonal mean shifts occur under the null hypothesis. When the magnitude of the breaks is large, simulation evidence reveals that, for three of the four testing procedures considered, the endogenously determined break point can be incorrectly estimated, resulting in spurious rejections of the null. A simple modification to one of the testing approaches is proposed which achieves a substantial improvement in test size

Single-photon-level sub-Doppler pump-probe spectroscopy of rubidium

We propose and demonstrate pump-probe spectroscopy of rubidium absorption which reveals the sub-Doppler hyperfine structure of the $^{5}$S$_{1/2} \leftrightarrow$ $^{5}$P$_{3/2}$ (D2) transitions. The counter propagating pump and probe lasers are independently tunable in frequency, with the probe operating at the single-photon-level. The two-dimensional spectrum measured as the laser frequencies are scanned shows fluorescence, Doppler-broadened absorption dips and sub-Doppler features. The detuning between the pump and probe lasers allows compensation of the Doppler shift for all atomic velocities in the room temperature vapor, meaning we observe sub-Doppler features for all atoms in the beam. We detail a theoretical model of the system which incorporates fluorescence, saturation effects and optical pumping and compare this with the measured spectrum, finding a mean absolute percentage error of 4.17\%. In the future this technique could assist in frequency stabilization of lasers, and the single-photon-level probe could be replaced by a single photon source.Comment: 5 page paper, 4 page supplemental material. Comments welcom

A well-conserved Plasmodium falciparum var gene shows an unusual stage-specific transcript pattern

The var multicopy gene family encodes Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) variant antigens, which, through their ability to adhere to a variety of host receptors, are thought to be important virulence factors. The predominant expression of a single cytoadherent PfEMP1 type on an infected red blood cell, and the switching between different PfEMP1 types to evade host protective antibody responses, are processes thought to be controlled at the transcriptional level. Contradictory data have been published on the timing of var gene transcription. Reverse transcription-polymerase chain reaction (RT-PCR) data suggested that transcription of the predominant var gene occurs in the later (pigmented trophozoite) stages, whereas Northern blot data indicated such transcripts only in early (ring) stages. We investigated this discrepancy by Northern blot, with probes covering a diverse var gene repertoire. We confirm that almost all var transcript types were detected only in ring stages. However, one type, the well-conserved varCSA transcript, was present constitutively in different laboratory parasites and does not appear to undergo antigenic variation. Although varCSA has been shown to encode a chondroitin sulphate A (CSA)-binding PfEMP1, we find that the presence of full-length varCSA transcripts does not correlate with the CSA-binding phenotype