Forecasting financial and macroeconomic variables using data reduction methods: New empirical evidence

In this paper, we empirically assess the predictive accuracy of a large group of models based on the use of principle components and other shrinkage methods, including Bayesian model averaging and various bagging, boosting, LASSO and related methods Our results suggest that model averaging does not dominate other well designed prediction model specification methods, and that using a combination of factor and other shrinkage methods often yields superior predictions. For example, when using recursive estimation windows, which dominate other windowing approaches in our experiments, prediction models constructed using pure principal component type models combined with shrinkage methods yield mean square forecast error best models around 70% of the time, when used to predict 11 key macroeconomic indicators at various forecast horizons. Baseline linear models (which win around 5% of the time) and model averaging methods (which win around 25% of the time) fare substantially worse than our sophisticated nonlinear models. Ancillary findings based on our forecasting experiments underscore the advantages of using recursive estimation strategies, and provide new evidence of the usefulness of yield and yield-spread variables in nonlinear prediction specification

Some Cautions Concerning Inferences about Proportions, Differences Between Proportions, and Quotients of Proportions

The purpose of this article is to bring to the attention of the educational research community several cautions regarding the use of inferential statistics for single proportions, differences between proportions, and quotients of proportions. The user of such procedures is urged to pay particular attention to the selection of the appropriate formula for the standard error and to the assumption of the independence of the observations

AFM of metallic nano-particles and nano-structures in heavily irradiated NaCl

AFM investigations are reported for heavily, electron irradiated NaCl crystals in ultra high vacuum (UHV) in the non-contact mode with an UHV AFM/STM Omicron system. To avoid chemical reactions between the radiolytic Na and oxygen and water, the irradiated samples were cleaved and prepared for the experiments in UHV. At the surface of freshly cleaved samples, we have observed sodium nano-precipitates with shapes, which depend on the irradiation dose and the volume fraction of the radiolytic Na. It appears that the nano-structures consist of (i) isolated nano-particles, (ii) more or less random aggregates of these particles, (iii) fractally shaped networks and (iv) ‘‘fabrics’’ consisting of bundles of Quasi-1D arrays forming polymeric networks of nano-particles. Almost independent of the concentration of the metallic Na in the samples the size of the individual nano-particles is in the range 1–3 nm. Our new AFM results are fully in line with our CESR and previous Raman scattering results.

Muscle: a source of progenitor cells for bone fracture healing

Bone repair failure is a major complication of open fracture, leading to non-union of broken bone extremities and movement at the fracture site. This results in a serious disability for patients. The role played by the periosteum and bone marrow progenitors in bone repair is now well documented. In contrast, limited information is available on the role played by myogenic progenitor cells in bone repair. In a recent article published in BMC Musculoskeletal Disorders, Liu et al. compared the presence of myogenic progenitor (MyoD lineage cells) in closed and open fractures. They showed that myogenic progenitors are present in open, but not closed fractures, suggesting that muscle satellite cells may colonize the fracture site in the absence of intact periosteum. Interestingly, these progenitors sequentially expressed a chondrogenic and, thereafter, an osteoblastic phenotype, suggestive of a functional role in the repair process. This finding opens up new perspectives for the research of orthopedic surgical methods, which could maximize myogenic progenitor access and mobilization to augment bone repair

Miniature Trailing Edge Effector for Aerodynamic Control

Improved miniature trailing edge effectors for aerodynamic control are provided. Three types of devices having aerodynamic housings integrated to the trailing edge of an aerodynamic shape are presented, which vary in details of how the control surface can move. A bucket type device has a control surface which is the back part of a C-shaped member having two arms connected by the back section. The C-shaped section is attached to a housing at the ends of the arms, and is rotatable about an axis parallel to the wing trailing edge to provide up, down and neutral states. A flip-up type device has a control surface which rotates about an axis parallel to the wing trailing edge to provide up, down, neutral and brake states. A rotating type device has a control surface which rotates about an axis parallel to the chord line to provide up, down and neutral states

How to interpret results of meta-analysis (Version 1.3)

Meta-analysis is a systematic method for synthesizing quantitative results of different empirical studies regarding the effect of an independent variable (or determinant, or intervention, or treatment) on a defined outcome (or dependent variable). Mainly developed in medical and psychological research as a tool for synthesizing empirical information about the outcomes of a treatment, meta-analysis is now increasingly used in the social sciences as a tool for hypothesis testing. However, the assumptions underlying meta-analytic hypothesis testing in the social sciences will usually not be met under real-life conditions. This is the reason why meta-analysis is increasingly conducted with a different aim, based on more realistic assumptions. That aim is to explore the dispersion of effect sizes

Introduction, comparison, and validation of Meta-Essentials

We present a new tool for meta‐analysis, _Meta‐Essentials_, which is free of charge and easy to use. In this paper, we introduce the tool and compare its features to other tools for meta‐analysis.We also provide detailed information on the validation of the tool. Although free of charge and simple, _Meta‐Essentials_ automatically calculates effect sizes from a wide range of statistics and can be used for a wide range of meta‐analysis applications, including subgroup analysis, moderator analysis, and publication bias analyses. The confidence interval of the overall effect is automatically based on the Knapp‐Hartung adjustment of the DerSimonian‐Laird estimator. However, more advanced meta‐analysis methods such as meta‐analytical structural equation modelling and meta‐regression with multiple covariates are not available. In summary, _Meta‐Essentials_ may prove a valuable resource for meta‐analysts, including researchers, teachers, and students

User manual for Meta-Essentials: Workbooks for meta-analyses (Version 1.3)

Meta-Essentials is a set of workbooks that facilitate the integration and synthesis of effect sizes from different studies and provide figures, tables, and statistics that might be helpful for interpreting them. Meta-Essentials generates (“overall” or “meta”) statistical information regarding a set of studies of the same phenomenon based on the statistical information from each separate study. The workbooks and a pdf-version of this user manual can be downloaded from [meta-essentials](http://www.erim.eur.nl/research-support/meta-essentials)

The UV Continuum of Quasars: Models and SDSS Spectral Slopes

We measure long (2200-4000 ang) and short (1450-2200 ang) wavelength spectral slopes \alpha (F_\nu proportional to \nu^\alpha) for quasar spectra from the Sloan Digital Sky Survey. The long and short wavelength slopes are computed from 3646 and 2706 quasars with redshifts in the z=0.76-1.26 and z=1.67-2.07 ranges, respectively. We calculate mean slopes after binning the data by monochromatic luminosity at 2200 ang and virial mass estimates based on measurements of the MgII line width and 3000 ang continuum luminosity. We find little evidence for mass dependent variations in the mean slopes, but a significant luminosity dependent trend in the near UV spectral slopes is observed with larger (bluer) slopes at higher luminosities. The far UV slopes show no clear variation with luminosity and are generally lower (redder) than the near UV slopes at comparable luminosities, suggesting a slightly concave quasar continuum shape. We compare these results with Monte Carlo distributions of slopes computed from models of thin accretion disks, accounting for uncertainties in the mass estimates. The model slopes produce mass dependent trends which are larger than observed, though this conclusion is sensitive to the assumed uncertainties in the mass estimates. The model slopes are also generally bluer than observed, and we argue that reddening by dust intrinsic to the source or host galaxy may account for much of the discrepancy.Comment: To be published in ApJ, 18 pages, 10 figure