### Book

## Теория вероятностей и статистика. Экспериментальное учебное пособие для 10-11 классов общеобразовательных учреждений.

This paper presents a method and computational technology for forecasting ambulance trips. We used statistical information about the number of the trips (per day or per night) in 2009-2013, the meteorological archive, and the corresponding archive of the meteorological measurements and meteorological forecasts for the same period. We take into account both social and meteorological predictors simultaneously. The impact of the meteorological factors (both climatic and short range lead times) into the statistics may be significant for some diseases. We present also the errors of these forecasts and demonstrate that the quality of our weather forecasts for the lead times 1- 3 days is good for the forecasting the number of ambulance trips.

The method may be used operatively for planning and control in the ambulance service. It may be applied for all trips and for specific subgroups of diseases. The method and the technology may be applied for any megalopolis if the corresponding medical and meteorological information is available.

This book is the textbook for the course "Probability theory and mathematical statistics", intended for students receiving higher education in Economics.

Authors investigate forming of transfer fee of professional football players. They analyze influence on its value factors, which define «human capital» of athlete, such as age, professional achievements and «level of publicity», i.e. his ability to attract spectators’ attention. It have been determined that strength of influence of professional achievements diminishes with age and taking into account «level of publicity» significantly rise quality of transfer fee modeling.

A simple measure of similarity for the construction of the market graph is proposed. The measure is based on the probability of the coincidence of the signs of the stock returns. This measure is robust, has a simple interpretation, is easy to calculate and can be used as measure of similarity between any number of random variables. For the case of pairwise similarity the connection of this measure with the sign correlation of Fechner is noted. The properties of the proposed measure of pairwise similarity in comparison with the classic Pearson correlation are studied. The simple measure of pairwise similarity is applied (in parallel with the classic correlation) for the study of Russian and Swedish market graphs. The new measure of similarity for more than two random variables is introduced and applied to the additional deeper analysis of Russian and Swedish markets. Some interesting phenomena for the cliques and independent sets of the obtained market graphs are observed.

The given paper proposes a method to assess credit worthiness based on a continuous scale. This method in contrast to current methods that rely on a binary scale such as bad/good credit uses aggregated randomized indices. Its application may have certain practical benifits in real life, e.g. assessing the individual loan price of a particular person rather than setting a standard loan price for clients. The credit scoring model is based on set of private borrowers information that can be converted into quality function corresponding to a weighting coefficient. These weighting coefficients and quality functions then can be used to compute the quality of credit score on a continuous scale. Results based on data from German credit base have showed the feasibility of the approach. It was found that results of credit scoring with a different scales can not be correctly compared by probability of well classified borrowers.

Measuring indirect importance of various attributes is a very common task in marketing analysis for which researchers use correlation and regression techniques. We have listed and illustrated some common problems with widely used latent importance measures. A more theoretically sound approach – the Shapley Value decomposition – was applied to a rich data set of US internet stores. The use of store-level data instead of respondent-level data allowed us to reveal the factors, which are powerful in explaining, why some stores have higher rates of willingness to make repeat purchases than the others. By confronting the indirect importance and performance measures for three different internet stores, we have revealed strengths, weaknesses, attributes that the company should bring customers’ attention to and attributes improvement of which is not of a high priority.

Let X be a semimartingale which is locally square integrable and admitting the canonical decompositions X=M+A and X=M ' +A ' with respect to measures P and P ' . Let γ be the density of A-A ' with respect to C=(〈M〉+〈M ' 〉) in the Lebesgue decomposition. Then there is a version h of the Hellinger process h(1/2;P,P ' ) such that (1-Δh) -2 ·h⪰(1/8)γ 2 ·C P- and P ' -a.s. This inequality is related with a generalization of the Cramér-Rao inequality to the case of filtered space. The author gives some applications to a continuous-time linear regression model as well as to a discrete-time autoregression model with martingale errors.

A model for organizing cargo transportation between two node stations connected by a railway line which contains a certain number of intermediate stations is considered. The movement of cargo is in one direction. Such a situation may occur, for example, if one of the node stations is located in a region which produce raw material for manufacturing industry located in another region, and there is another node station. The organization of freight traﬃc is performed by means of a number of technologies. These technologies determine the rules for taking on cargo at the initial node station, the rules of interaction between neighboring stations, as well as the rule of distribution of cargo to the ﬁnal node stations. The process of cargo transportation is followed by the set rule of control. For such a model, one must determine possible modes of cargo transportation and describe their properties. This model is described by a ﬁnite-dimensional system of diﬀerential equations with nonlocal linear restrictions. The class of the solution satisfying nonlocal linear restrictions is extremely narrow. It results in the need for the “correct” extension of solutions of a system of diﬀerential equations to a class of quasi-solutions having the distinctive feature of gaps in a countable number of points. It was possible numerically using the Runge–Kutta method of the fourth order to build these quasi-solutions and determine their rate of growth. Let us note that in the technical plan the main complexity consisted in obtaining quasi-solutions satisfying the nonlocal linear restrictions. Furthermore, we investigated the dependence of quasi-solutions and, in particular, sizes of gaps (jumps) of solutions on a number of parameters of the model characterizing a rule of control, technologies for transportation of cargo and intensity of giving of cargo on a node station.

Let k be a field of characteristic zero, let G be a connected reductive algebraic group over k and let g be its Lie algebra. Let k(G), respectively, k(g), be the field of k- rational functions on G, respectively, g. The conjugation action of G on itself induces the adjoint action of G on g. We investigate the question whether or not the field extensions k(G)/k(G)^G and k(g)/k(g)^G are purely transcendental. We show that the answer is the same for k(G)/k(G)^G and k(g)/k(g)^G, and reduce the problem to the case where G is simple. For simple groups we show that the answer is positive if G is split of type A_n or C_n, and negative for groups of other types, except possibly G_2. A key ingredient in the proof of the negative result is a recent formula for the unramified Brauer group of a homogeneous space with connected stabilizers. As a byproduct of our investigation we give an affirmative answer to a question of Grothendieck about the existence of a rational section of the categorical quotient morphism for the conjugating action of G on itself.

Let G be a connected semisimple algebraic group over an algebraically closed field k. In 1965 Steinberg proved that if G is simply connected, then in G there exists a closed irreducible cross-section of the set of closures of regular conjugacy classes. We prove that in arbitrary G such a cross-section exists if and only if the universal covering isogeny Ĝ → G is bijective; this answers Grothendieck's question cited in the epigraph. In particular, for char k = 0, the converse to Steinberg's theorem holds. The existence of a cross-section in G implies, at least for char k = 0, that the algebra k[G]G of class functions on G is generated by rk G elements. We describe, for arbitrary G, a minimal generating set of k[G]G and that of the representation ring of G and answer two Grothendieck's questions on constructing generating sets of k[G]G. We prove the existence of a rational (i.e., local) section of the quotient morphism for arbitrary G and the existence of a rational cross-section in G (for char k = 0, this has been proved earlier); this answers the other question cited in the epigraph. We also prove that the existence of a rational section is equivalent to the existence of a rational W-equivariant map T- - - >G/T where T is a maximal torus of G and W the Weyl group.