The Beta-Hyperbolic Secant (BHS) Distribution

The shape of a probability distribution is often summarized by the distribution's skewness and kurtosis. Starting from a symmetric parent density f on the real line, we can modify its shape (i.e. introduce skewness and in-/decrease kurtosis) if f is appropriately weighted. In particular, every density w on the interval (0; 1) is a specific weighting function. Within this work, we follow up a proposal of Jones (2004) and choose the Beta distribution as underlying weighting function w. Parent distributions like the Student-t, the logistic and the normal distribution have already been investigated in the literature. Based on the assumption that f is the density of a hyperbolic secant distribution, we introduce the Beta-hyperbolic secant (BHS) distribution. In contrast to the Beta-normal distribution and the to Beta-Student-t distribution, BHS densities are always unimodal and all moments exist. In contrast to the Beta-logistic distribution, the BHS distribution is more êexible regarding the range of skewness and leptokurtosis combinations. Moreover, we propose a generalization which nests both the Beta-logistic and the BHS distribution. Finally, the goodness-of-fit between all above-mentioned distributions is compared for glass fibre data and aluminium returns. --

Taxation and the Demand for Gambling: New Evidence from the United Kingdom.

In October 2001, the U.K. government implemented a dramatic shift in the taxation of gambling, resulting in a substantial decline in taxes levied on U.K. bookmakers. Using data before and after this event, we present econometric evidence on the demand response to this tax reduction. Our results suggest that the demand for bookmaker gambling is highly sensitive to taxation rates and that the decline in the rate of taxation led to a large increase in the demand for on-shore betting. We also find some evidence of price-induced substitution across different segments of the gambling industry. The U.K. policy initiative may provide useful information for policy makers in other countries who are contemplating changes in gambling taxation.

SWOT Analysis of the horticultural farms in the Plovdiv region of Bulgaria

Agriculture/horticulture has traditionally been an important sector in the economy of Bulgaria. This paper reviews the changes in agriculture/horticulture in the Plovdiv region of Bulgaria after 1989 when the transition towards a free market economy began. In particular, it provides a review of the internal capabilities (strengths and weaknesses) of the horticultural farms and the impact upon them of the external environment (opportunities and threats). While many farmers regarded their experience as a strength, farmers having farms of different size identified additional different strengths, and different weaknesses and opportunities. Whereas, all of them were influenced by similar threats and the relative importance of these perceived threats did not varied depending upon the size of the farm

'Quarbs' and Efficiency in Spread Betting Markets: can you beat the book?

In this paper, we examine a relatively novel form of gambling, index (or spread) betting, that mirrors (and indeed overlaps with) practices in conventional financial markets. In this form of betting, a number of bookmakers quote a bid-offer spread about the result of some future event, and bettors are invited to buy (sell) at the top (bottom) end of the quoted spreads. We hypothesise that the existence of an outlying spread may provide uninformed traders with information that can be used to develop improved trading strategies. Using conditional moment tests on data from a popular spread betting market in the United Kingdom, we find that in the presence of a number of price-setters, the market mid-point is indeed a better predictor of asset values than the outlying price. We further show that this information can be used to develop trading strategies that lead to returns that are consistently positive and superior to those from noise trading and, in some cases, significantly so.

Non-extremal black hole solutions from the c-map

We construct new static, spherically symmetric non-extremal black hole solutions of four-dimensional ${\cal N}=2$ supergravity, using a systematic technique based on dimensional reduction over time (the c-map) and the real formulation of special geometry. For a certain class of models we actually obtain the general solution to the full second order equations of motion, whilst for other classes of models, such as those obtainable by dimensional reduction from five dimensions, heterotic tree-level models, and type-II Calabi-Yau compactifications in the large volume limit a partial set of solutions are found. When considering specifically non-extremal black hole solutions we find that regularity conditions reduce the number of integration constants by one half. Such solutions satisfy a unique set of first order equations, which we identify. Several models are investigated in detail, including examples of non-homogeneous spaces such as the quantum deformed $STU$ model. Though we focus on static, spherically symmetric solutions of ungauged supergravity, the method is adaptable to other types of solutions and to gauged supergravity.Comment: 57 pages. Minor changes to the introduction, typos corrected and references added. Accepted for publication in JHE

The Combined Release and Radiation Effects Satellite (CRRES) program: A unique series of scientific experiments

The Defense Department and NASA have joined in a program to study the space environment which surrounds the earth and the effects of space radiation on modern satellite electronic systems. The Combined Release and Radiation Effects Satellite (CRRES) will carry an array of active experiments including chemical releases and a complement of sophisticated scientific instruments to accomplish these objectives. Other chemical release active experiments will be performed with sub-orbital rocket probes. The chemical releases will 'paint' the magnetic and electric fields of earthspace with clouds of glowing ions. Earthspace will be a laboratory, and the releases will be studied with an extensive network of ground-, aircraft-, and satellite-based diagnostic instruments. Some of the topics discussed include the following: the effects of earthspace; the need for active experiments; types of chemical releases; the CRRES program schedule; international support and coordinated studies; photographing chemical releases; information on locating chemical releases for observation by the amateur; and CRRES as a program

The Beta-Hyperbolic Secant (BHS) Distribution

The shape of a probability distribution is often summarized by the distribution's skewness and kurtosis. Starting from a symmetric parent density f on the real line, we can modify its shape (i.e. introduce skewness and in-/decrease kurtosis) if f is appropriately weighted. In particular, every density w on the interval (0; 1) is a specific weighting function. Within this work, we follow up a proposal of Jones (2004) and choose the Beta distribution as underlying weighting function w. Parent distributions like the Student-t, the logistic and the normal distribution have already been investigated in the literature. Based on the assumption that f is the density of a hyperbolic secant distribution, we introduce the Beta-hyperbolic secant (BHS) distribution. In contrast to the Beta-normal distribution and the to Beta-Student-t distribution, BHS densities are always unimodal and all moments exist. In contrast to the Beta-logistic distribution, the BHS distribution is more êexible regarding the range of skewness and leptokurtosis combinations. Moreover, we propose a generalization which nests both the Beta-logistic and the BHS distribution. Finally, the goodness-of-fit between all above-mentioned distributions is compared for glass fibre data and aluminium returns

The empirical accuracy of uncertain inference models

Uncertainty is a pervasive feature of the domains in which expert systems are designed to function. Research design to test uncertain inference methods for accuracy and robustness, in accordance with standard engineering practice is reviewed. Several studies were conducted to assess how well various methods perform on problems constructed so that correct answers are known, and to find out what underlying features of a problem cause strong or weak performance. For each method studied, situations were identified in which performance deteriorates dramatically. Over a broad range of problems, some well known methods do only about as well as a simple linear regression model, and often much worse than a simple independence probability model. The results indicate that some commercially available expert system shells should be used with caution, because the uncertain inference models that they implement can yield rather inaccurate results